Chemistry International

256 Pages·1996·17.7 MB·English

ISSN 0193-6484
The news magazine of the International Union
of Pure and Applied Chemistry (IUPAC)
.
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y
1996, Vol. 18, No. 1 (January)
Blackwell
Science
DafieraiaGIteiiiall
The news magazine of the International Union of Pure
and Applied Chemistry (IUPAC)
EDITOR: Jeffrey H. Williams
SECRETARIAL ASSISTANTS: Mary Patterson and Katie Smith
PRODUCTION EDITOR: Howard Waller
All correspondence to be addressed to The Editor, Chemistry International, IUPAC Secretariat, Bank Court
Chambers, 2-3 Pound Way, Templars Square, Cowley, Oxford 0X4 3YF, UK. Telephone: [phone].
Fax: [phone]. E-mail: [email protected]
Editorial Advisory Board
Chairman: E. D. BECKER Secretary-General G. SOMSEN Division 1
E. BUNCEL CHEMRAWN Committee K. L. KOMAREK Division II
S. R. HELLER Committee on Chemical Databases M. M. MIKOLAJCZYK Division III
T. D. CULPIN Committee on Chemistry and Industry A. D. JENKINS Division IV
D. H. M. BOWEN Committee on Publications M. PARKANY Division V
1. M. MILLS Interdivisional Committee on T. R. ROBERTS Division VI
Nomenclature and Symbols H. P. LEHMANN Division VII
M. E. PESTANA Commitee on Teaching of Chemistry C. G. WERMUTH Medicinal
Chemistry
Secretary. J. H. WILLIAMS Editor Section
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Front cover: Istanbul: Aya Sofya (Hagia Sophia—the Church of the Holy Wisdom) built 532-537AD in the reign of the Emperor
Justinian. Before it became a Mosque (after the Turkish conquest) it was the largest Christian Church, it is now a museum.
International Union of Pure and Applied Chemistry
Istanbul 1995
The 35th Biennial Congress of the International Union for
Pure and Applied Chemistry, organised in 1995 by the
Turkish Chemical Society, was held in Istanbul at the
Swissotel.
The hosting city, Istanbul—previously known as Con¬
stantinople, is the only city in the world built on two con¬
tinents. The city stands on the shores of the Bosphorus
where the waters of the Black Sea mingle with the Sea
of Marma. On its truly majestic site, Istanbul contains zantium was all that remained of the Byzantine Empire.
the relics and splendour of the three empires of which it The city was finally captured by the Ottoman Sultan
has been the capital. Mehmed the Conqueror (II) on 29 May 1453, who
Byzantium was a Greek town, founded by the refounded Byzantium as a Muslim city.
Megarian King Byzas, which had been in existence for This was, however, not the end of the success of the
nearly nine centuries when it was chosen, in 330, by the city as the Turkish conquerors created the Ottoman
Roman Emperor Constantine as his new capital city in Empire which dominated the Middle-East and Eastern
the East of the Roman Empire; for political and military Europe until the beginning of the present century and
reasons he had decided to break the Roman Empire established their capital in Constantinople. However,
definitively into two halves. Rome was the capital of the with the dismemberment of the Ottoman Empire after
Western Empire and the refounded Byzantium was to the First World War, Constantinpole, which had by
be the capital of the Eastern Empire. Indeed, when the know become Istanbul, remained one of the great cos¬
Empire in the west was over run by barbarian armies in mopolitan cities of the Mediterranean.
the 5th century, and after Rome had been sacked by It is ironical in that the Turkish name for the city is
the Vandals, the Roman Empire continued in the East perhaps a corruption of the medieval Greek words ‘ ‘s tin
with Byzantium becoming ‘New Rome’ and maintaining polin’, which may be translated as ‘going to town’—a
Roman culture and civilization. However, the Roman familiar expression for those who live near a large town
Empire was by this time a Christian Empire, and the or city. The Greeks insist that the name of the city be
original Latin tongue of Constantine had been replaced Contantinople, a word never used by their Byzantine
by the Greek language. The city becoming the center of ancestors, but used by their Arab enemies and by the
the Orthodox Faith. Prophet himself in the form Konstantiniye. Others say
This Byzantine Empire continued to flourish for the that Istanbul is a corruption of the Turkish expression
next nine centuries reaching its apogee in the 10th ‘Islambof—where Muslims are plentiful. Whatever, the
Century under the Emperor Basil Bulgaroctonus (II) origin of its modern name, the city dominated the imagi¬
when the population of the city protected by its massive nations of medieval people, the Slavs referred to the
5th century walls, almost 15 km in length, was well in city as Tsarigard—the Emperor’s city; and the Norse¬
excess of one million, at a men called it
time when Paris and Lon¬ Micklegarth—the
don were relatively insig¬ place between
nificant villages. However, earth and the
with the advent of the Cru¬ abode of the gods.
sades, the Byzantine Em¬ The opening cer-
pire was weaken from
strife with Western Euro¬
peans, the Western Prof. A. Riza
Church and the Islamic Berkem, President
World. With foes pressing of the 35th IUPAC
Congress and
from all sides, the empire
President of the
continued to shrink and
Turkish Chemical
eventually the city of By¬ Society.
Chemistry International, 1996, Vol. 18, No. 1 1
emony of the 35th IUPAC Congress was held on the
Monday morning in the ATATURK KULTUR MERKEZI.
The Organizing Committee, represented by Profs A.R.
Berkem and B. Baysal spoke in English and welcomed
the delegates to Istanbul. The Mayor and Governor of
Istanbul both spoke in Turkish and repeated the wel¬
come of the Organizing Committee. Prof. A.E. Fischli,
Dr Faruk Demiray,
Vice-President of the Union, spoke on behalf of IUPAC
Member of the
and introduced the Union to the delegates. Prof. Fischli Organizing Committee
described IUPAC, its history, its goals and spoke of of the 35th IUPAC
how it goes about achieving these important tasks; he Congress and
Secretary General of
spoke about lUPAC’s funding and about the numerous
the Turkish Chemical
important international collaborations within which
Society.
IUPAC is involved. The final comments at this cer¬
emony of welcome were from the President of the Turk¬
and/or 1-2 Molar HN03. In addition, the exchange ma¬
ish Republic, His Excellency Suleyman Demirel, who
terials must have high selectivity for the ions of interest,
had sent a message of welcome which was read, in as the solutions will contain high levels of a variety of
both Turkish and English, to the delegates.
salts. Under these conditions, organic resins are not
The organising committee of the 35th IUPAC Con¬
suitable and one must move to new inorganic materials.
gress put together a scientific programme which cov¬
The synthesis and structure of a variety of layered
ered a wide variety of different fields of chemistry, a
and tunnel structures was described. These included
wide ranging survey of the present state of knowledge
several new titanates and zirconates, phosphates,
and future trends in six areas of chemistry.
silicophosphates, titanosilicates and pharmacosider-
The opening ceremony was followed by a short inter¬
ites. The high selectivity of these exchange materials
mission, after which the scientific programme began.
recommends them for use in industrial and nuclear en¬
vironments.
Human needs through chemistry
• Environment;
Physical chemistry, dynamics and
• Food;
structure
• Energy;
• Health;
• Fast chemical processes;
The Food Chemistry section contained one invited
• Energy transfer;
lecture (from Europe), three oral presentations and 39
• State-to-state chemistry;
posters. In the section on Health Chemistry, there were
• Multiphoton and multiple photon excitation;
two invited lectures (US and Canada), 14 oral presenta¬
• Mode-selective chemistry;
tions and 76 poster presentations. In Energy, there
• Theoretical calculations of reaction surfaces;
were three invited lectures (all from the US), 5 oral pres¬
• Chemical kinetics;
entations and 16 poster presentations. In the Environ¬
• Molecular thermodynamics;
mental Chemistry section, there were two invited
• Computational chemistry;
lectures ( both from Turkey), 14 oral presentations and
• Laser and molecular beams;
97 poster presentations.
• Corrosion and its prevention.
One of the interesting posters in the section on Envi¬
The Physical Chemistry section of the Congress con¬
ronmental chemistry came from the group of Prof
tained six invited lectures, three from Europe, one from
Abraham Clearfield at Texas A&M University, Texas,
the Middle East and two from the US. In addition, there
USA, relating to the design of new ion exchange mate¬
were 30 oral presentations and 183 poster presenta¬
rials which could operate under adverse conditions—
tions. Of this total number of presentations, over half
Ion exchange materials for nuclear and environmental
came from chemists in the geographical region of Tur¬
waste remediation.
key and the Middle East, and another 31% came from
There is a continuing need for stable selective ion
Asia.
exchange materials for nuclear and industrial waste
Of particular interest was the lecture by Prof. R.D.
treatment. In the case of nuclear waste resulting from
Levine (Fritz Haber Research Center for Molecular Dy¬
weapons production, ion exchange materials have to
namics, The Hebrew University, Jerusalem) who spoke
be stable to high energy particles and to very corrosive
on the current developments in molecular reaction dy¬
chemical environments, for example, 1-3 Molar NaOH
namics—Molecular reaction dynamics looks towards
2
Chemistry International, 1996, Vol. 18, No. 1
Ferries wait to carry passengers
across the Bosporus.
the next century: understanding complex systems. Polymer science and high technology
The speaker showed how reaction dynamics is mak¬ materials
ing increasing contact with real chemical systems by
• New methods of polymerization;
examining: elaborate reaction mechanisms typical of
• Structure and properties of macromolecules;
organic chemistry, the study of chemical reactions
• Solution properties of macromolecules;
where the medium plays an active part (as is often the
• Engineering polymers and high performance materi¬
case on surfaces and in solution) and the mimicking of
als;
systems of biochemistry.
• Polymeric blends and networks;
Much of the early conceptual ideas in this field came
• Liquid crystalline polymers;
from the study of isolated, simple chemical exchange
• Novel polymers have biological significance.
reactions where one chemical bond is broken as an¬
In the Polymer and Materials Chemistry section of
other is formed. A central feature of such reactions is
the Congress there were nine invited lectures, five from
the high selectivity which can be achieved by the
Europe, one from the US, one from the Middle East and
choice of initial conditions and the specificity of the
two from Asia. In addition, there were 39 oral presenta¬
products. For example, the specificity of the energy dis¬
tions and 181 posters. Of this total number of presenta¬
persal of exoergic reactions—those that can produce
tions, almost two thirds came from chemists in the
chemical lasers. Prof. Levine pointed out that such
geographical region of Turkey and the Middle East, and
ideas can now be increasingly carried over to more
another 25% came from Asia.
complex systems.
Analytical chemistry and instrumentation
Organic chemistry, synthesis,
mechanisms and natural products
• Computer based analytical methods;
• Electroanalytical methods;
• Bio-organic chemistry;
• Atomic spectrometry;
• Organometallic chemistry;
• Molecular spectroscopy;
• Physical organic chemistry, organic electrochemis¬
• Analytical separations and chromatography;
try;
• Analytical separations in clinical science, analytical
• Organic photochemistry;
automation;
• Biosynthesis;
• Optical, electrochemical, acoustic, biological, and
• Identification of natural products;
other sensors;
• Natural products with potential pharmacological ac¬
• Chemometrics, enzymatic techniques, capillary
tivities.
electrophoresis;
In Organic chemistry, there were eight invited lec¬
• Surface analysis;
tures, three from Europe, two from the US, two from the
• Flow injection analysis.
Middle East and one from Asia. In addition, there were
In Analytical Chemistry, there were nine invited lec¬
71 oral presentations and 204 posters. Of this total
tures, six from Europe, two from the Middle East and
number of presentations, over half came from chemists
one from the US. In addition, there were 33 oral presen¬
in the geographical region of Turkey and the Middle
tations and 129 poster presentations. Of this total
East, and another 28% came from Asia.
Chemistry International, 1996, Vol. 18, No. 1 3
est is the role of the nitride ion, which
has a high polarizability and may
therefore cause specific properties in
structure and bonding. The important
step in the investigation of these ma¬
terials was the use of elemental nitro¬
gen as an oxidizing agent for
intermetallic melts.
Also of interest was an invited talk
by Norman N. Greenwood (The Uni¬
versity of Leeds, Leeds, UK)—Recent
developments concerning the discov¬
ery of elements 101-110.
Professor Greenwood spoke of the
ten newest elements (Z= 101-110)
and their subsequent troubled history.
How the preparation of these ele¬
Sultanahmet Camii (Blue Mosque) Built in the reign of Sultan Ahmet I ments required outstanding feats of
(1603-1618).
intellectual and experimental virtuos¬
ity—only a few short lived atoms are
number of presentations, over half came from chemists produced in several weeks of experimenting. However,
in the geographical region of Turkey and the Middle some of the discoveries have been widely accepted,
East, and another 24% came from Asia. but others have been hotly contested.
There were five Plenary Lectures, a summary of
these excellent and informative talks are given below:
Inorganic chemistry and solid state
Jack G. Calvert (National Center for Atmospheric
• Intermetallic compounds; Chemistry, USA)
• New advanced inorganic materials; The Chemistry of the Atmosphere, Its Perturbations
• Coordination chemistry, electrochemistry of coordi¬ Through Human Activities
nation compounds; The chemistry of the atmosphere results from a com¬
• Bio-inorganic chemistry; plex series of chemical reactions that involve many at¬
• Inorganic photochemistry and photoelectrochemis¬ mospheric trace gases and which are initiated through
try; sunlight absorption by ozone, formaldehyde and other
• Organometallic and cluster chemistry; molecules which are present in the atmosphere in
• Rare earth chemistry; minute amounts. Within the troposphere, this complex
• Optoelectronics, crystals, thin films; photochemistry forms ozone and many other reactive
• Condensed phase chemistry; intermediates including acids and peroxides. In con¬
• Catalysts and related subjects; trast, stratospheric chemistry leads to the destruction of
• Superconductors, semiconductors, organic conduc¬ natural stratospheric ozone—our protective shield
tors, solid state ionic conductors. against hard ultraviolet solar radiation. This lose arises
In the Inorganic Chemistry section of the Congress, when halocarbons, normally unreactive compounds in
there were four invited lectures, one from Europe and the troposphere, are released at the surface of the
three from Asia. In addition, there were 41 oral presen¬ Earth and are ultimately transported to the strato¬
tations and 153 posters. Of this total number of presen¬ sphere. Here sunlight dissociated the halocarbons into
tations, over half came from chemists in the highly reactive species that start chain reactions which
geographical region of Turkey and the Middle East, and can destroy atmospheric ozone.
another 22% came from Asia. Of current interest is the design and operation of en¬
Of particular interest was an invited talk by Rudiger vironmentally friendly supersonic aircraft for the 21st
Kniep (Eduard-Zintl-lnstute, TH-Darmstadt, Germany) century. Such new aircraft will have the same problem
on a new class of inorganic materials—Ternary and posed by the Anglo-French Concorde in the early
Quaternary Metal Nitrides: A new challenge for solid 1970s, namely, the effect of the planes’ nitrogen radical
state chemistry. emissions on the ozone layer through which the plane
Compared with the large number of well known flies. In the stratosphere, nitric oxide and nitrogen diox¬
oxometalates, the crystal structure and chemistry of ide take part in complex catalytic reaction cycles that
nitridometallates is still in its infancy. Of particular inter¬ were previously thought to be the dominant process for
ozone destruction throughout most of the lower strato-
4
Chemistry International, 1996, Vol. 18, No. 1
sphere. Consequently, the greater the number of air¬ 30%. The reaction set
craft travelling through the ozone layer the greater the
BrO + CIO -> Br + Cl + 02
destruction.
Recent measurements reveal however that in the
Br + 03 -> BrO + 02
lower stratosphere (16-20 km altitude) the effect of ni¬
trogen oxides on ozone is far outweighed by the ozone
Cl + 03 -> CIO + 02
destroying reactions of hydrogen containing radicals,
hydroxyl (OH) and hydroperoxyl (H02) and the halogen Net: 203 -» 302
containing radicals such as chlorine monoxide (CIO)
is responsible for 20-25% of the halogen controlled
and bromine monoxide (BrO). Small additions of nitro¬
loss. Finally,
gen radicals at those altitudes actually decreases the
loss of ozone because the nitrogen containing radicals O + CIO -» Cl + 02
react with the hydrogen and halogen containing radi¬
cals thereby short circuiting their destructive effect. Cl + 03 -» CIO + 02
However, the impact on total ozone concentrations is
uncertain due to the complexity of circulation and mix¬ Net: O + 03 -» 202
ing models in the stratosphere.
accounts for 5% of ozone loss by halogen chemistry at
Central to these new insights into nitrogen radical
15km altitude, increasing to 25% at 21 km altitude. The
chemistry in the lower stratosphere are simultaneous
formation of CION02 and BrON02 leads to ozone loss
measurements of the concentrations of all of the fami¬
through photolysis of N03 followed by the above reac¬
lies of radicals that are involved in ozone destruction.
tion. These processes account for 10-15% of the halo¬
In contrast to earlier models that predicted a much
gen controlled loss rates.
more important role for NOx catalysis, the cycles:
NO + 03 -> N02 +02 Richard R. Ernst (ETH, Zurich, Switzerland)
Exploring the Structure and Dynamics of Molecules
N02 + O -> NO + 02 Through Nuclear Magnetic Resonance
Prof. Ernst began his lecture pointing out that 1995 was
Net: 03 + O -» 202 an anniversary year for scientists interested in struc¬
tural studies. It was in 1945 that the first Nuclear Mag¬
and
netic Resonance (NMR) spectra were obtained; a tech¬
NO + 03 -> N02 + 02 nique which is now one of the most versatile means of
obtaining detailed molecular information on dynamics
N02 + 03 -> N03 + 02 and structure. However, we are in addition to this anni¬
versary celebrating the centenary of the discovery of x-
N03 + light -> NO + 02 rays; the other technique which gives detailed struc¬
tural information. Prof. Ernst used his talk to demon¬
Net: 203 -> 302
strate the versatility of NMR for the study of the dynam¬
ics and structure of a number of small polypeptide (ten
account for less than 20% of the total ozone loss.
amino acids), and how the observed molecular dynam¬
As a result of the enormous quantity of halocarbons
ics change with experimental conditions. For example,
dumped into the atmosphere over the last few decades,
he demonstrated how the conformation of a cyclic
nearly one-third of the photochemical loss of ozone is
decapeptide (antanamide), which from statistical argu¬
due to reactions involving CIO and BrO radicals. The
ments could assume any one of thousands of possible
most important processes are:
conformations, could be locked into one particular
H02 + ZO -> HOZ + 02
structure by a single water molecule which rapidly ex¬
changed between polar side grouped on the
HOZ + light -> OH + Z
polypeptide. NMR being the ideal tool for probing such
dynamics.
Z + 03 -> ZO + 02
Similarly, whereas X-rays can show you where the
side chained dangling from a polypeptide attach them¬
OH + 03 -> H02 + 02
selves to another cellular component, X-rays cannot tell
you the timescale on which this interaction is taking
Net: 203 -> 302
place. One can obtain a ‘snap shot’ of the overall struc¬
where Z = Cl accounts for about 30% of halogen con¬ ture, but with X-rays one cannot look into the nature of
trolled loss and Z = Br accounts for between 20 and the interactions.
Chemistry International, 1996, Vol. 18, No. 1 5
The speaker pointed out that the first NMR spectra electron jumps from one ion to the other instantane¬
gave little information of use to chemists, indeed, the ously while the ions and their associated solvent
early NMR scientists were all physicists or mathemati¬ sheaths take a finite time to relax to the electron trans¬
cians. However, with the development of multi-dimen¬ fer. That is, the separation of electronic and nuclear
sional Fourier transform NMR over the last 30 years, motion—the nuclear configuration readjusts after the
chemists can now obtain detailed information on inter- electronic transition, and not during it. Consequently
molecular and intramolecular structure and dynamics. the dielectric polarization of the medium cannot be
Indeed, NMR has recently developed into a leading di¬ treated as a continuum, the solvent molecules have
agnostic tool for the medical sciences, and is now an discrete orientations around the ion and are changing
expensive item on one’s hospital bill. these orientations, consequently, ideas of
In some ways the techniques of NMR and X-rays are nonequilibrium polarization have to be incorporated
complimentary, however, they are also two competing into a statistical model of the jump process. To power
tools for investigating similar properties. NMR is tradi¬ the jump, one can consider an incident light source,
tionally used to probe large molecules in solution however, Marcus pointed out long ago that electron
where, for example, biological molecules are active - transfer reactions occur in the dark and that it is thermal
one can study the proteins in action. X-rays, however, fluctuations in the solvent which are the driving force for
give poorly resolved structural information on liquids, the electron to jump from one ion to the other—essen¬
but give structures of the molecules in the solid state - tially a tunnelling process which requires relatively little
X-rays cannot study protein function. Both NMR and X- energy.
rays can be used to determine crystal structure, X-rays The theory of electron transfer also shows why elec¬
have been used for this type of study in small molecules tron transfer processes in photobiology must be very
since the First World War. However, with large mol¬ fast—there are numerous competing processes on a
ecules of biological importance, for example, proteins, longer timescale. For example, the chromophore ab¬
NMR can be used to determine structures of molecules sorbs a photon, thereby exciting an electron. On a na¬
ranging in size up to the kilodalton mass range—the nosecond timescale this excited electron can fluoresce,
smaller end of the protein market. X-rays, however, can or it can couple to the vibrational ladder of states
be used to investigate the structure of the very largest through a intramolecular vibrational energy transfer
proteins—megadalton mass range. process and lose energy this way. Consequently, the
longer the excited electron hangs around, the greater
Rudolph A. Marcus (California Institute of the probability that it will lose energy—energy which will
Technology, USA) not be available latter on for chemical synthesis. Within
Electron Transfer in Chemistry and Biology: Theory
a protein molecule there is no solvent sheath so the
and Experiment
electron transfer process is very fast—there is only an
Prof. Marcus demonstrated how the field of electron
electronic component, no solvent reorganization.
transfer reactions has grown considerably from the late
Prof. Marcus concluded his talk with a discussion on
1940s and early 1950s. During that period, the rates of
the theory of electron transfer within proteins. In this
many isotope exchange electron transfer reactions
theory, an artificial intelligence method has been devel¬
were determined using radioactive isotopes which had
oped for selecting the amino acids most important for
recently become available. Such reactions represented
the intramolecular electron transfer, for use in the cal¬
the simplest case of all chemical reactions, and elec¬
culation of the donor-acceptor electron transfer cou¬
tron transfer reactions in particular. Since this time
pling factor. Such a procedure greatly reduces the
when electron transfer reactions were considered a
computational difficulties. Experimental studies of such
‘dusty corner’ of a very specialized field of solution
systems are now becoming almost routine with the
chemistry, the electron transfer field has grown to in¬
technology of molecular biology. Selected site
clude many areas: inorganic reactions in solution; or¬
mutagenesis allows one to make proteins with donor
ganic reactions; reactions at metal/liquid, semiconduc¬
and acceptor groups in particular places in their struc¬
tor/liquid and liquid/liquid interfaces, and at modified
ture—controlling the distance over which the electron
electrodes; photoinduced electron transfers (solar en¬
has to jump. It is found that the rate or ability of the
ergy conversion, charge transfer spectra of donor-ac¬
electron transfer depends upon electron rich pathways
ceptor systems); and biological electron transfers as in
between donor and acceptor groups.
photosynthesis.
All these many branches of chemistry can be ration¬
Richard E. Smalley (Rice University, USA)
alized with simple theoretical ideas, for which Prof.
Fullerene Nanowires
Marcus was awarded the 1992 Nobel prize in chemis¬
We are currently hearing a great deal about molecular
try. Such ideas include the application of Franck-
electronics, where chemists are synthesising and as¬
Condon principle to electron transfer, that is, that the
sembling new molecules which will have the
6
Chemistry International, 1996, Vol. 18, No. 1
electrochemical properties of very much larger pieces particle, the diameter of the graphene tube and the
of inorganic semiconducting material. However, what of pressure of inert gas in the arcing device a number of
future developments? One of the prerequisites of a vi¬ products are possible. If the metal particle diameter is
able nanoscale device is a means of conducting the very much greater than 1 pm and with an inert gas pres¬
electron from one part of the nano-device to another sure of an atmosphere, the main product of the arcing is
without it going to ground, a short circuit. That is, how graphite. If the metal particles are smaller than a few
do you make a nanowire? nanometers and at pressures less than an atmosphere,
At a molecular level, the transfer of an electron re¬ then diamond is the main product of the arcing process.
quires overlap of donor electronic orbitals with those of However, for metal particles slightly smaller than a mi¬
the acceptor. Due to the usual atomic localization of cron and at pressures less than or equal to an atmos¬
orbitals, this desired overlap is a strong function of the phere, carbon nanotubes are produced in large
distance between donor and acceptor. But the overlap quantity. What appears to be happening is that carbon
can be effectively extended by incorporating an inter¬ dissolves in the metal particles and precipitates out of
vening material which itself overlaps with both the do¬ the metal on the growing nanotube which is attached to
nor and acceptor orbitals. Molecular electricians are the metal particle.
currently seeking nano-conductors that confer struc¬ Appropriate chemical substitutions inside and/or out¬
tural rigidity, preventing spatial arrangements which side these nanostructures offer an array of rationally
lead to molecular short circuits. designed new materials including semiconductors, su¬
Prof. Smalley, one of the discoverers of C60, pointed perconductors, nanowires and catalysts.
out that a single graphite sheet, a graphene layer com¬
posed of carbon in a hexagonal lattice, would have an Frank E. Karasz (University of Massachusetts,
enormous tensile strength—perhaps a 100 times USA)
Electroluminescense in n-conjugated polymers
greater than steel, being a single molecule even though
Prof. Karasz described the synthesis of multi-block al¬
it might have macroscopic dimensions. Such sheets
ternating copolymers of rigid phenylene vinylene units
provide the only known example where atoms of a sin¬
of specified length interspersed with flexible spacer
gle element combine to produce a chemically passive
groups of methylene or of ethylene oxide oligomers.
two dimensional surface. If pentagons are incorporated
These materials are soluble and film forming, and by
into such a sheet it will being to assume positive curva¬
varying the chromophore length and/or by
ture. With 12 pentagons, the surface closes to give a
derivatization can be tuned to provide electro-lumines¬
fullerene which may be either spherical (C60) or tubular
cence at specified wavelengths to essentially cover the
(nanotube).
entire visible spectrum. The electrodes in a typical ar¬
If heptagons are incorporated into a graphene sheet,
rangement are indium-tin oxide and Al, Ca, Mg or Ag;
then negative curvature will be given to the two dimen¬
the active polymer matrix is, of order, 100 nm thick and
sional surface. Prof. Smalley outlined
the driving voltages are about 10-30 V.
nanotechnologies based on the addition of pentagons
Karasz demonstrated how the luminescence varied
and heptagons to graphene sheets to produce a variety
with the nature of blends of these copolymers, and with
of new materials which would be chemically resistant
mixtures containing other chromophorically active mac¬
and very strong. He went on to outline the production of
romolecules. Greatly improved quantum efficiency can
nanotubes which would have walls a single carbon
be obtained by adopting different configurations and
atom thick (1 nm in diameter), but would be many thou¬
incorporating electron and/or hole transport layers.
sands of times longer. Such tubes would be conduc¬
Charge injection under reverse bias also leads to light
tors, but if doped, as is done in graphite intercalates,
emission under certain conditions and to further under¬
with Na or Cs they would become exceptional conduc¬
standing of the photophysics of these new materials.
tors.
This Congress was not as well attended as previous
To produce these tubes has been something of a
IUPAC congresses, there were about 800 delegates.
‘black art’, they are produced to varying degrees with
There was a small exhibition of industrial organizations,
the carbon arcs used to produce fullerenes. However,
including the official publisher of the Union—Blackwell
the optimal conditions have only been found be trial and
Science Ltd.
error. Prof. Smalley outlined a model for the optimal
What was noticeable however was the strong boost
production. It was known that small amounts of Fe or Ni
this Congress has given to local or regional chemists. It
catalyzed the production of the nanotubes—how was
was apparent that a great many of the delegates were
something of a mystery. Smalley’s model is that small
from the Middle East and Asia, there were some chem¬
particles of the metals attach themselves to the open
ists from the United States and Western Europe, how¬
end of a curved graphene sheet—preventing the cap
ever, they were very much in the minority.
from closing. Depending on the diameter of the metal
Chemistry International, 1996, Vol. 18, No. 1 7
Thirteen million - and still growing
For Chemical Abstracts Service, 1994 was a year of unprecedented database growth and im¬
proved delivery of information, IUPAC affiliate Dr W. Val Metanomski reports.
The theme for Chemical Abstracts Service (CAS) activi¬ in 1994. The list of 192 countries, where the reported
ties in 1994 might well have been ‘bigger and better’, work was done, included such countries as Cyprus (9
reflecting both the expanded volume of information papers), Fiji (5 papers), Grenada (2 papers), Mozam¬
processed and the improved, more timely, accessibility bique (2 papers), Namibia (3 papers), and Samoa (2
on-line. papers).
First, consider the raw numbers. During 1994, CAS In terms of language, in 1994, papers published in
abstracted and indexed 653 055 papers, patents, and English rose to 81.9% (from 69.2% in 1984 and 73.8%
other publications. This was an all time annual record in 1989), followed by Russian (5.2%), Chinese (4.6%),
well over the previous high number of 553 051 in 1991. and Japanese (4.2%). The contributions in German
In addition, CAS cited 122 752 equivalent patents in showed a marked decrease (1.5%, down from 3.4% in
1994. 1984), and so did those in French (0.6%, down from
An all time record was also noted in the growth of the 1.3% in 1984). Among lesser-known languages, within
CAS Chemical Registry System. In 1994, 777 212 new the total of 49 languages in which papers were pub¬
chemical substances were added to the System, again lished, are: Cambodian, Georgian, Kazakh, Sinhalese,
well over the previous high number of 690 313 in 1992. Thai and Uzbek.
CAS milestones for the year included the registration Within the 107 226 patents abstracted in 1994 (an¬
of the 13-millionth chemical substance and the publica¬ other annual record), the Japanese again had the larg¬
tion of the 15-millionth abstract. est share (61.0%), followed by USA (8.5%), the
The 13-millionth chemical substance registration European Patent Office (EPO) (8.3%), and the World
was a synthetic polymer, a novel poly(amide imide), Intellectual Property Organization (WIPO) (8.0%). The
reported in a paper by three German researchers at the equivalent patents cited in CA showed a somewhat dif¬
University of Freiburg, H. A. Schneider, N. Steinhauser, ferent distribution: Japan (30.6%), EPO (20.1%), USA
and R. Mulhaupt (CA 121 (2), 10424x) (see below). (13.5%) and Canada (8.4%).
The 15-millionth CA abstract, published in March With respect to changes in different chemical fields in
1994, reported on ‘Fire- and dripping-resistant resin the past five years, while the total number of abstracts
compositions’, patented by two Japanese researchers, increased 33.5%, the greatest increase occurred in the
Y. Mishima and R. Yoneyama {CA 120 (12), 136218f). Applied Chemistry and Chemical Engineering Sections
In 1994, the largest share of the journal literature (41.8%), followed by that in the Biochemistry Sections
again came from USA (29.2%), followed by Japan (38.4%). Focusing on more specific subdisciplines,
(12.7%), Germany (6.6%), People’s Republic of China within the Biochemistry Sections, the largest increases
(6.2%), United Kingdom (5.5%), and Russia (4.6%). were noted in the fields of biochemical genetics; radia¬
The most noticeable upward change was in the number tion biochemistry; nonmammalian biochemistry; mam¬
of papers originating from the People’s Republic of malian pathological biochemistry; immunochemistry;
China, from 8797 in 1984, to 14 748 in 1989, to 33 684 and fertilizers, soil, and plant nutrition.
Fig. 1 Poly[(1,3-dihydro-1,3-dioxo-2H-isoindole-2,5-diyl)[2,2,2-trifluoro 1-(trifluoromethyl)ethylidene](1,3-dihydro-1,3-
dioso-2W-isoindole 5,2-diyl)-1,3-phenyleneimino(2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro 1,8-dioxo-1,8-octanediyl)imino-1,3-
phenylene] [1155827-99-91],
8
Chemistry International, 1996, Vol. 18, No. 1