Light Absorption of Organic Colorants: Theoretical Treatment and Empirical Rules

254 Pages·1980·5.5 MB·English

by  Jürgen Fabian

Reactivity and Structure
Concepts in Organic Chemistry
Volume 12
Editors:
Klaus Hafner lean-Marie Lehn
Charles W. Rees P. von Rague Schleyer
Barry M. Trost Rudolf Zahnradnik
J. Fabian H. Hartmann
Light Absorption
of Organic Colorants
Theoretical Treatment
and Empirical Rules
With 76 Figures and 48 Tables
Springer-Verlag
Berlin Heidelberg New York 1980
Jiirgen Fabian
Horst Hartmann
Sektion Chemie der Technischen UniversWit Dresden
Mommsenstr. 13
DDR-8027 Dresden
List of Editors
Professor Dr. Klaus Hafner
Institut fur Organische Chemie der TH
Petersenstr. 15, D-6100 Darmstadt
Professor Dr. Jean-Marie Lehn
Institut-de Chimie, Universite de Strasbourg
1, rue Blaise Pascal, B. P. 296/R8, F-67008 Strasbourg-Cedex
Professor Dr. Charles W. Rees, F. R. S. Hofmann
Professor of Organic Chemistry, Department of Chemistry
Imperial College of Science and Technology
South Kensington, London SW7 2A Y, England
Professor Dr. Paul v. R. Schleyer
Lehrstuhl fur Organische Chemie der Universitat Erlangen-Niirnberg
Henkestr. 42, D-8520 Erlangen
Professor Barry M. Trost
Department of Chemistry, The University of Wisconsin
1101 University Avenue, Madison, Wisconsin 53706, U.S.A
Prof. Dr. Rudolf Zahradnik
Tschechoslowakische Akademie der Wissenschaften
J .-HeyrovskY-Institut fur Physikal. Chemie und Elektrochemie
Machova 7, 12138 Praha 2, C.S.S.R.
ISBN-l3: 978-3-642-67589-8 e-ISBN-13: 978-3-642-67587-4
DOl: 10.1007/978-3-642-67587-4
Library of Congress Cataloging in Publication Data. Fabian Jiirgen, 1936-.
Light absorption of organic colorants. (Reactivity and structure; v. 12). Bib
liography: p. Includes index. 1. Dyes and dyeing - Chemistry. 2. Color. I.
Hartmann, Horst, 1937-joint author. II. Title. III. Series. QD441. F3.
547.8'6. 80-12452
This work is subject to copyright. All rights are reserved, whether the whole or
part of the material is concerned, specifically those of translation, reprinting,
re-use of illustrations, broadcasting, reproduction by photocopying machine
or similar means, and storage in data banks. Under § 54 of the German Copy
right Law where copies are made for other than private use, a fee is payable
to the publisher, the amount of the fee to be determined by agreement with
the publisher.
© by Springer-Verlag Berlin Heidelberg 1980
Softcover reprint of the hardcover 1st edition 1980
2152/3140-54321 0
Preface
Although studies on synthetic dyes have been performed for more than 100 years, their
detailed elucidation requires further extensive research. The discovery of novel high
polymers, the necessity of supplying a whole range of shades and increasing require
ments for dyestuffs of high fastness properties give rise to a permanent search for new
dyes. Extensive investigations on dyes were also occasioned by various applications in the
field of spectral sensitization and of staining of biological specimens. Another more
recent development concerns the lasing properties of some organic dyes. Most of the
progress, however, was only achieved by time-consuming, purely empirical approaches
and theoretical understanding of the dye properties is only at its very beginnings.
The color is the sine qua non of every dye. For this reason organic chemists and
color chemists have looked for relations between the "color and constitution" of dye
molecules for a long time. This knowlege as a whole is known as "theory of color".
The classic theory of color was established abou t 100 years ago by Witt and was signi
ficantly extended 50 years later by W. Konig.
With the production of highly efficient UV-VIS spectrophotometers and the de·
velopment of appropriate quantum chemical methods, the theory of color received
new impulses. Some classic concepts were proved to be based on wrong assumptions,
but many of the rules and relationships derived could be explained. Moreover, they
were extended, and predictions even became possible about the color of structures for
which any empirical experience is lacking. The better understanding of the electronic
structure of the dye molecules, in tum, permits one to tackle theoretically further un·
solved problems of color chemistry.
This book reviews the absorption features of organic dyes and recent progress in
their explanation in terms of molecular structure. Originally we intended a more de
tailed description both of the basic chromophoric system and of the theoretical
methods which render possible the derivation of color-structure relationships. Since
the book became too voluminous we decided after fruitful discussions with the editor
to restrict the introductory chapter to a brief outline.
In the first five chapters only basic problems and fundamental theoretical ap
proaches are mentioned. Here a conception js advanced as to how the relate the dif
ferent fields of experience and how to assess possibilities and limits of some qualitative
and quantitative theories. For the sake of brevity, the application of the different ap
proaches is not described in detail, but references are made to examples discussed later
on.
v
Preface
The chapters VI to XV deal with the spectral characteristics of various organic
colorants encompassing naturally occurring as well as synthetic dyes. As far as possible
the spectral shifts are accounted for by theoretical models.
Although the compilation of spectral data had to be selective, we have tried to
illustrate the full range of accessible absorption wavelengths by modifying the respec
tive 'chromophoric system.
The book is mainly intended for organic chemists and color chemists which are
interested in the spectral characteristics of dyes and their conceptual understanding.
It is hoped that it will also be useful as source of data to spectroscopists and theoret
icians, whose support is needed for the further development of the theory on color
structure relationships.
The writing of this book was suggested by Prof. Dr. R. Zahradnik (Czechoslovak.
Academy of Science) to whom we are indebted for encouragement and many helpful
discussions.
For helpful dicussions and critical reading of the manuscript we would also like to
express our gratitude to Dr. S. Diihne (Academy of Science, GDR) , Dr. M. Nepras
(Institute of Organic Synthesis, Pardubice, CSSR), Prof. Dr. R. Mayer and Dr. A. Mehl
horn (Technical University of Dresden). We are also grateful to Mrs. Brigitte Friebe for
her skilled assistance in preparing the manuscript.
Dresden, Spring 1980 J. Fabian
J.Hartmann
VI
Table of Contents
I. Phenomenological Conceptions on Color and Constitution .......... .
II. UV/VIS Spectroscopy and Quantum Chemistry of Organic Colorants. . . . 3
III. Relation Between Phenomenological and Quantum Chemical Theories . . . 9
IV. Theoretical Methods for Deriving Color-Structure Relationships. . . . . . .. 14
1. PPP-CA Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
2. LHM Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16
3. FMO Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 18
V. Classification of Organic Colorants. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
VI. Polyene Dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24
1. Chromophoric System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 24
2. Carotenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27
3. Retinal and Derivatives .................................. 30
4. Diarylpolyenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 32
5. Polyenes Bridged by Heteroatoms ... . . . . . . . . . . . . . . . . . . . . . . .. 39
6. Medium Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40
VII. Azo Dyes ........................................... 42
1. Chromophoric System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 42
2. Weak Long Wavelength Absorptions. . . . . . . . . . . . . . . . . . . . . . . . .. 43
3: Azo Compounds with Carbocyclic Groups. . . . . . . . . . . . . . . . . . . . .. 46
4. Substituted Azobenzenes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 50
5. Polykisazo Compounds ...... . . . . . . . . . . . . . . . . . . . . . . . . . . .. 60
6. Heterocyclic Azo Compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 62
7. Tautom~ric Azo Compounds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 68
8. Medium Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 74
VIII. Carboximide, Nitro and Quinacridone Dyes . . . . . . . . . . . . . . . . . . . .. 80
VII
Table of Contents
IX. Quinoid Dyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89
1. Chromophoric System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89
2. Weak Long-Wavelength Absorptions. . . . . . . . . . . . . . . . . . . . . . . . .. 90
3. Benzoquinones and Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 92
4. Annelatedpara-Benzoquinones and Derivatives .................. 100
5. Higher Annelated Quinones ............................... 110
6. Medium Effects ....................................... 112
X. Indigoid Dyes ........................................ 115
1. Chromophoric System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 115
2. Indigo and Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 123
3. Indigo-like Compounds .................................. 128
4. Medium Effects ....................................... 133
XL Diphenylmethane, Triphenylmethane and Related Dyes. . . . . . . . . . . .. 137
1. Chromophoric System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 137
2. Unsubstituted Monoaryl, Diaryl and Triarylmethane Dyes and Vinylogues. 138
3. Substituted Arylmethane Dyes and Heterocyclic Analogous . . . . . . . . .. 143
4. Heteroanalogous Arylmethane Dyes and Heteroatom-Bridged Derivatives . 155
5. Medium Effects ....................................... 159
XIL Polymethine Dyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 162
1. Chromophoric System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 162
2. Symmetrical Polymethine Dyes. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 167
3. Unsymmetrical Polymethine Dyes . . . . . . . . . . . . . . . . . . . . . . . . . .. 178
4. Dyes with Substituted, Bridged and Coupled Chains . . . . . . . . . . . . . .. 183
5. Branches Polymethine Dyes ............................... 190
6. Medium Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 192
XIII. Porphyrins and Phthalocyanines ............................ 198
XlV. Conjugated Betaine Dyes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 205
Xv. MUltiple Chromophore Dyes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 212
References .............................................. 215
Subject Index ............................................ 241
VIII
1. Phenomenological Conceptions on Color and
Constitution
Dyestuffs have been used for thousands of years. Until the beginning of this century,
indigo, alizarin, and further dyestuffs were produced from plant and animal materials.
The origin of the color of organic substances could only be successfully explained
when the molecular constitution of the first dyes had been established and the first syn
theses carried out.
We shall not analyze in detail the various concepts which have arisen during the last
100 years in order to explain color, and the exciting pros and cons. Most textbooks of
color chemistry describe the historical development and several review papers cover this
subject [1-4]. We should mention here a few concepts which in our opinion have signifi
cantly contributed to the theory of color-structure relationships.
The first relations between color and molecular constitution can be traced back to
Graebe and Liebermann [5], who related the color of organic substances to a system of
unsaturated bonding. About one decade later, after the elucidation of the constitution
of several dye molecules, Witt [6] founded the "classical theory of color". He attributed
the visual color to the presence of particular groups, the "chromophores". Structures
containing chromophores were termed as "chromogens". When the chromophores is
colorless itself, so called "auxochromic groups" may give it color. Chromophores in the
original sense were, e.g., N=O, N=N, C=C, C=O, and auxochromes NH2, OH etc.
Witt's theory of color was extended and refined in the course of this century by
Kaufmann [7], Dilthey, and Wizinger [8-11]. During this time the meaning of the terms
chromophore and auxochrome underwent considerable change [12]. The term "anti
auxochromes" was newly introduced for groups which induce a brightening of the color
[8]. Antiauxochromes are e.g. N=O or C=O, i.e. groups which formerly belonged to the
chromophores. Wizinger attributed the color of organic colorants to the presence of intra
molecular ionic states, which were modelled by coupling of auxochromes and antiauxo
chromes with conjugated systems.
These approaches obviously consist in a partitioning of the whole conjugated systems
of the dye molecule into several molecular building blocks. Although the explanations
given in the Witt-Dilthey-Wizinger's color theory later proved to be less satisfactory or
even completely wrong, the idea of molecular partitioning retained much of its appeaL
Thus Griffiths most recently has regarded important synthetic dyes as being composed
of donor and acceptor fragments ("donor-acceptor chromogens") [13].
On the other hand, already soon after the foundation of Witt's theory of color also
concepts were developed which clearly contrast with those just mentioned. In these con-
Phenomenological Conceptions on Color and Constitution
cepts the color was attributed to larger conjugated bond systems as a whole. Thus
Nietzky [14] and Armstrong [15] related the color to quinoid structures. According to
them, triphenylmethane dyes owe their color to quinoid substructures. Von Baeyer
[16] assumed, moreover, an oscillation between quinoid and benzenoid ring systems.
Along the same lines, Willstiitter and Piccard [17] defined the "meriquinoid state", attri
buting to each benzene ring of triphenylmethane some quinoid character. According to
Iz'mailskii [18] dyes molecules exist in a "mesotropic equilibrium state" which gives
rise to the color ("chromo-state"). This conception resembles to the later introduced
and widely used mesomerism approach [19] and its equivalent presentation in terms of
quantum mechanical resonance [20]. The color-determining conjugated system has now
been generally designated the "chromophore" [12].
Color-determining conjugated systems, however, are not exclusively cyclic struc
tures. Already early studies pointed out that some colored compounds contain chain
molecules [21]. Later Konig [22] recognized the basic polymethine chromophore. He
defined polymethines as chain molecules contail).ing an odd number of me thine or
heteroanalogous groups ("mesochrome") and terminal groups ("perichromes"). These
structures give rise to the "chromo-state". According to Konig the chromo-state is char
acterized by a high degree of bond equalization and charge alternation along the con
jugated chain. The terminal perichromes are monovalent groups. They determine
whether the dye molecule is neutral or ionic. The cationic streptopolymethine-cyanine
and the anionic streptopolymethine-oxonols, for example, encompass equal perichromes,
the neutral streptopolymethine-merocyanine two different ones.
More recently Diihne and coworkers [23-28, 28a] revived and refined Konig's theory
of color. They gave a generalized definition of the polymethine state and directed the
chemist's attention to the occurrence of polymethine building blocks in various organic
dyes. According to them polymethinic subunits are the essential part of every organic
dyestuff. Hiinig and Quast independently demonstrated the importance of polymethine
chains in an excellent review paper on newer colored systems [29].
All the above mentioned concepts of the classic theory of color are phenomeno
logical in essence, based on the chemist's experience and intuition ("chemical theories").
Although each concept possesses its own features, there is one prinCiple inherent in all
conceptions: the deeply colored compounds contain conjugated bonds. The whole con
jugated system is, in principle, responsible for the color. But the color can also often
be rationalized alternatively by assembling the conjugated system from chromophoric
subunits. The latter approach has an appreciable heuristic value: a great variety of chro
mophores can be conceived by combination of only a few basic chain and cyclic sub
chromophores.
2