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The temperature dependence of the 2 E g - 4 A 2g phosphorescence of tetrabutylammonium hexacyanochromate (III) dissolved in various solvents has been measured within the liquid range of these solvents. In this limited temperature range, the reciprocal decay times obey Arrhenius relationship. From the absence of a solvent isotope effect, in ethanol and methanol and their monodeuterated analogues it is concluded that hydrogen bonds between the solvent and the complex ion do not provide promoting or accepting modes for the radiationless deactivation. The room temperature decay times have been found to correlate with the solvatochromic shift of the 4 A 2 g − 4 T 2 g absorption bands and with Dimroth's E T parameter. According to the selection rules for non-radiative decay a combination of CN stretching with either a Cr-C-N bending or a Cr-C stretching vibration is postulated as the promoting mode.

The products of condensation of 1,2-dimethylisoquinolinium and 1,2-dimethyl-3,4-dihydroisoquinolinium salts with salicylaldehyde derivatives may, depending on the nature of the substituents, exist in the merocyanine or spiropyran form. The spiropyrans of the dihydroisoquinoline series are considerably more stable than the isoquinoline analogs. In polar solvents the spiropyrans of both series exist in equilibrium with the corresponding merocyanine, and the position of the equilibrium depends on the Z function of the solvent and is shifted more strongly to favor the merocyanines in the case of isoquinoline derivatives. The merocyanines of both series have negative solvatochromism, but the solvent effect is greater by a factor of 1.5-2 for the dihydroisoquinoline derivatives.

Dyes suitable for passive switching in the generation of ultrashort pulses in ruby lasers were synthesized and investigated. Two groups of polymethine dyes were studied: 1) Cation cyanines; 2) electron–neutral merocyanines. The absorption spectra and cross sections of these dyes were determined. The shifts resulting from the replacement of the solvent (solvatochromism) were found. Suitable dye — solvent combinations were tested as passive switches under Q-switching and mode-locking conditions. The characteristics of the output radiation obtained using these switches were determined.

Der Vergleich der Komplexreihen LMo(CO)4, LMo(CO)3PBu3 und LMo(CO)2(PBu3)2 [L = t-C4H9NCHCHNt-C4H9 (DAB); 2,2′-Bipyridyl (bpy)] und ihrer paramagnetischen Monoanionen zeigt, das die π-Akzeptorfahigkeit von bpy nur etwa halb so gros ist wie die von DAB. Das ergibt sich aus den Spindichten an den Koordinationszentren und den 31P-Kopplungen im ESR sowie aus der Solvatochromie der Absorptionen in den Elektronenspektren. Die π-Wechselwirkung (β) erreicht fur bpy nur ca. 0.6 eV, fur DAB 1 eV. The Complex Chemistry of Four Center π Systems, IX. 2,2′Bipyridyl– a „Bad Ligand” for Metals in Low Oxidation States The comparison of the complex series LMo(CO)4, LMo(CO)3PBu3, and LMo(CO)2(PBu3)2 [L = t-C4H9NCHCHNt-C4H9 (DAB), 2,2′-bipyridyl (bpy)] and their paramagnetic monoanions reveals that the π-acceptor quality of bpy is only about one half of that of DAB. This follows from EPR spin densities at the coordination sites and 31P coupling constants as well as from the solvatochromism of the absorption in the electronic spectra. π-Interaction (β) is for bpy approximately 0.6 eV, while it reaches 1 eV for DAB.

Derivate des 2,3-Dichlormaleinsaure-anhydrids, die als Heteroatom im Funfring S, C (als ) und N (als bzw. )enthalten, wurden mit Diphenyl(trimethylsilyl)phosphin in die jeweiligen 2,3-Bis(diphenylphosphino)-Derivate (3–6) ubergefuhrt, die als zweizahnige Liganden zwei CO in den Carbonylen von Ni, Cr und Mo substituieren konnen (7–14). Die freien Liganden und ihre Metallcarbonyle sind intensiv farbig. Die entsprechenden Absorptionsbanden zeigen einen betrachtlichen Einflus des Heteroatoms im Funfring an. Weiterhin wurde die Solvatochromie der langwelligsten Absorptionsbande in den Metallcarbonylderivaten untersucht. Zu Vergleichszwecken wurden ferner 2,3-Bis(diphenylamino)-N-methylmaleinimid (15) und zwei Diphenyl-phosphinoderivate (16, 18) des 3,4-Dichlor-5-methoxy-2(5H)-furanons erstmals dargestellt. Die Zuordnung von vcc ist nunmehr in allen diesen Verbindungen moglich. Ihre bis zu 120 cm−1 betragende Verschiebung und die Abhangigkeit der Farben der Verbindungen von der Ausdehnung des konjugierten Systems werden diskutiert. Synthesis and Properties of Derivatives fo 2,3-Bis(diphenylphosphino)maleic Anhydride as a Contribution to the Problem of Colour, Conjugation, and complex Formation of this Class of Compounds Derivatives of 2,3-bis(diphenylphosphino)maleic anhydride containing S, C (as ) and N (as or ) as heteroatom within the ring system (3–6) are prepared from the corresponding 2,3-dichloro compounds with the aid of diphenyl(trimethylsilyl)phosphine. These new compounds form chelate complexes of the type Ni(CO)2. L, Cr(CO)4-L (7–14). Ligands and complexes are strongly coloured. The heteroatom of the maleic anhydride ring influences remarkably the corresponding absorption bands. The solvatochromic effect on the low wave number absorption band of the metal(O) complexes is examined. For comparison 2,3-bis(diphenylamino)-N-methylmaleimide (15) and two diphenylphosphino derivatives (16, 18) of 3,4-dichloro-5-methoxy-2(5H)-furanone are synthesized. The vcc bands of the compounds are assigned. The observed shifts (up to 120 cm−1) and the dependence of the colour on the size of the conjugated system are discussed.

A large bathochromic shift is reported for the charge-transfer (CT) transition in complexes of π-electron donors with electron acceptors containing CO groups in strongly H-bonding solvents such as trifluoroacetic acid and hexafluoroisopropanol. The results of 13C-NMR measurements and SCF-LCAOMO calculations indicate that this effect can be attributed to an increased electronegativity of the acceptor upon hydrogen bond formation with the solvent.

The solvatochromic merocyanine dye I is found by spectroscopic techniques to have a pK a = 8.57 in the ground state and pK * a = 1.85 in the lowest excited singlet state. The validity of the Forster cycle for compounds of this sort is discussed in terms of molecular distortions occurring upon excitation that are indicated both spectrally and by quantum chemical calculations.

The title compounds and related substances were prepared, characterised and tested as solvatochromic chelating agents. These reagents show large color changes with solvent, and the chelates, though insoluble in most common solvents, are also solvatochromic. Reagents with a 2-methyl group adjacent to the chelating centre do not precipitate aluminium, and this effect can be used as a colour test for aluminium.

Empirical parameters of solvent polarity E T of some pure solvents and their binary mixtures (especially with CCl4 and CHCl3) were determined spectrophotometrically using solvatochromic pyridinium-N-phendl betaine dyes. Calibration curves are given for 16 binary solvent mixtures. The obtained E T values show that a synergetic polarity effect appears with the organic solvents containing C=O, P=O, and S=O groups in the mixture with chloroform. With these binary mixtures the increase of E T values results from the formation of 1∶1 complexes X=O... H-CCl3 by means of hydrogen bonding. Increasing number of methylene groups in the chain increases the synergism with these type of complexes.

The different photochromic systems which have been used in polymer chemistry are mainly based on cis-trans isomerization of azomethines and azocompounds which were built into the polymeric backbone, or attached as sidegroups. These systems are reviewed and briefly commented upon. Special attention is paid to spirobenzopyran derivatives of which the photochromism is very important and characterized by a strong negative solvatochromism. Different spirobenzopyran photochrome-containing polymers are considered: (1) copolymers with vinyl monomers, e.g. methyl methacrylate-styrene. (2) polypeptides such as polytyrosine and polylysine. (3) polycondensation products. Their behaviour in solution is discussed and the existence of different isomeric mesoxy amines demonstrated. In the solid state when these photochromes are used in a polymeric matrix, they permit detection of secondary glass transition phenomena; by contrast, when attached on a copolymer, they permit accurate determination of T g . In crosslinked systems the copolymers show a reversible photochromic behaviour. Finally a comparison of these photochromic phenomena with thermal racemization of some new optically active polymers is presented.

1.4-Diaza-butadiene-(1.3) bilden mit Kupfer(I)-halogeniden stark farbige, monomere 1:1-Komplexe 2-11, 16-20, 24, 25 mit dreifach koordiniertem Kupfer. Diese Koordination bestimmt das elektronenspektroskopische Verhalten. Wahrend in Diazabutadien-Komplexen anderer Metalle in niedrigen Oxydationsstufen die langstwellige Absorption sehr starken Metall-Ligand-charge-transfer-Charakter hat, fehlt hier bei etwa gleich starker Beteiligung von Metalltermen im Grundzustand und angeregten Zustand die typische Solvatochromie und die extrem hohe Intensitat des farbgebenden Ubergangs. Copper(I)-diazabutadiene Halides 1,4-Diazabuta-1,3-dienes react with cuprous halides to form strongly coloured, monomeric 1:1 adducts 2-11, 16-20, 24, 25, containing copper with threefold coordination. This coordination number determines the spectroscopic behaviour. While diazabutadiene complexes of other metals in low oxidation states show a long-wavelength absorption with strong metal-to-ligand CT character, in the copper complexes 2-11, 16-20, 24, 25 the metal terms are about equally important in the ground and excited state without showing the typical solvatochromism and the extremely high intensity of the chromogenic transition.

Aus 2.3-Dichlomaleinsaureanhydrid und Diphenyl(trimethylsilyl)phosphin dargestelltes 2,3-Bis(diphenylphosphino)maleinsaureanhydrid kann als zweizahniger Ligand in Carbonylen des Ni, Cr, Mo und W zwei CO substituieren. Die so dargestellten Komplexe sind luftbestandig und uberraschend tieffarbig; ihre bei ∼17500 cm−1 beobachtete Absorptionsbande zeigt einen starken Solvatochromieeffekt. 1,2-Bis(diphenylphosphino)cyclobutendion konnte nur in Ni(CO)4 unter Substitution von zwei CO eingefuhrt werden. Die Charakterisierung der orangefarbenen kristallinen Verbindung wird durch ihre extreme Lichtempfindlichkeit erschwert. Dagegen bildet 1-(Diphenylphosphino)-2-phenylcyclobutendion als einzahniger Ligand L stabile Komplexe vom Typ M(CO)5L mit MCr, Mo. 2,3-Bis(diphenylphosphino)maleic Anhydride and Diphenylphosphino Derivatives of Cyclobutenedione as Ligands in Metal Carbonyls 2,3-Bis(diphenylphosphino)maleic anhydride is prepared from 2,3-dichloromaleic anhydride and diphenyl(trimethylsilyl)phosphine. With this compound as a bidentate ligand the complexes Ni(CO)2L and M(CO)4L (MCr, Mo, W) are obtained. These are stable and deeply coloured, dut to an absorption band in the region of 17500 cm−1 which shows a strong solvatochromic effect. With 1,2-bis(diphenylphosphino)cyclobutenedione as ligand L only the complex Ni(CO)2L could be prepared, with immediately decomposes at ligand forms stable complexes of the type M(CO)5L (MCr, Mo).

The position and the intensity of electronic bands are influenced by an electric field. Pronounced changes in the position of absorption bands are mainly due to the dipole moment of the molecule in the ground state and the change in the dipole moment during the excitation process, and pronounced changes in intensity are due to the field dependence of the transition moment, which can be described by the transition polarizability. The effect of an external electric field on the optical absorption (electrochromism) of suitable molecules can be used to determine the dipole moment in the ground state, the change in dipole moment during the excitation process, the direction of the transition moment of the electronic band, and certain components of the transition polarizability tensor. These data largely determine the strong solvatochromism (solvent-dependence of the position and intensity of electronic bands), which is observed in particular with molecules having large dipole moments. Smaller contributions to solvatochromism result from dispersion interactions, which predominate in the case of nonpolar molecules. The models developed have been experimentally checked and verified by a combination of electro-optical absorption measurements (influence of an external electric field on absorption) and investigation of the solvent-dependence of the electronic bands.

The charge–transfer absorption spectra of the title compound have been measured for seven solvents at 25°C over the pressure range 1–1960 kg/cm2. The effect of the solvents on the shift of λmax with pressure was remarkable in a series of alcohols. The λmax for methanol and ethanol shifted to the red, while for the other alcohols it shifted to the blue. This may be one of the interesting behavior based on the hydrogen bonding between the solute and the solvents.

The kinetics of aquation of bis(2,2′;6′,2″-terpyridyl)iron(II), [Fe(terpy)2]2+, have been examined in aqueous solution, and a mechanism consistent with the observed pH–rate profile proposed. Activation parameters for fission of the first iron–nitrogen bond have been determined and compared with those for related complexes. The rate law for reaction of [Fe(terpy)2]2+ with cyanide ion is as in equation (i). Activation parameters for the –d[Fe(terpy)22+]/dt=k9+k10[CN–][Fe(terpy)22+](i), k10 path, which is the dominant reaction route, are compared with those for analogous second-order reactions of similar iron(II) complexes with cyanide ion. Solvatochromic behaviour is reported for the [Fe(terpy)(CN)3]– anion, the primary product of the reaction of [Fe(terpy)2]2+ with cyanide.

1-Methyl-2-[2-(8-hydroxy-5-quinolyl)vinyl]-8-hydroxyquinolinium chloride has been prepared as an example of a chelating agent for metals that changes colour with solvent polarity. As a chelating agent it has some selectivity, precipitating only the copper II ion in an acidic solution and forming a distinctively coloured product with zinc in neutral solutions. In ammoniacal methanol it gives a red solution with magnesium and several other ions. A number of related solvatochromic compounds have also been prepared.

The condensation of o-aminothiophenol with tetrahydroacetophenone, 2-ethylidenecyclohexanone, and 2-benzylidenecyclohexanone and also the condensation of N-methyl-o-aminothiophenol with 2-benzylidenecyclohexanone has given the bases of derivatives of benzo[b]cyclohexano[f]- and -[e]-1,4-thiazepines. From the hydrochlorides, perchlorates, and quaternary salts of these bases, cyanine dyes have been synthesized. The dyes—norcyanines—exhibit solvatochromism, which is explained by the existence of a hydrogen bond between the molecules of the dye and an alcohol.

Es werden einige mononukleare und binukleare Chelatkomplexe von Metallcarbonylen der 6. Nebengruppe mit Azomethinen des Pyridincarbaldehyds beschrieben, sowie Phosphin- und Phosphitderivate dieser Chelatkomplexe. Das spektrale Verhalten der Verbindungen wird mit dem ahnlich strukturierter 1,4-Diazabutadien- und Dipyridylkomplexen verglichen. Alle untersuchten Chelatkomplexe zeigen eine starke negative Solvatochromie in organischen Losungsmitteln und in polymeren Matrizen. Solvatochromism of Subgroup VI Metal(0) Complexes with Bidentate Azomethine Ligands Some mononuclear and binuclear chelat compounds of azomethines, derived from the carbonyls of molybdenum and chromium are described. The spectrophotometrical behaviour of the compounds is compared with the behaviour of the diazabutadiene and dipyridyl metalcarbonyls. The complexes show strong negative solvatochromic effects in organic solutions and in polymers.

The absorption spectra in the vapour phase, in cyclohexane and methanol solutions of para -substituted benzylidenemethylamines have been measured and discussed in terms of solvatochromic and substituent effects. A comparison with the absorption spectra of benzylideneanilines of the p -R. · C 6 H 4 · CH : N · C 6 H 5 type confirms that these compounds have a non-planar conformation with the aniline ring twisted out of the C 6 H 5 · CH : N · plane.

Mit Hilfe der solvatochromen Pyridinium-N-phenol-betaine 4a, 4b und 4e wird die fruher beschriebene Losungsmittelpolaritatsreihe fur 29 Losungsmittel erweitert (Tabelle 1). Pyridinium-N-phenol Betaines and their Application for the Characterization of Solvent Polarities, VI. Extension of the Solvent Polarity Scale by Determination of New ET Values With the aid of the solvatochromic pyridinium-N-phenol betaines 4a, 4b and 4e the formerly described solvent polarity scale is extended for 29 solvents (table 1).

The ground state dipole moment of the π-electrons of 2.4.6-triphenyl-N- [3.5-di-tert-butyl-4-hydroxy-phenyl] -pyridinium-betain I, a highly solvatochromic substance, was determined by measuring the dielectric constant of a dilute solution and calculating first the dipole moment of the whole system (σ- and π-electrons) using the method of HALVERSTADT and KUMLER. The dipole moment of the π-electrons was then calculated, asuming the π-electron dipole to be imbedded in a spherical medium of dielectric constant 2. The value calculated by this method was compared with the π-electron dipole moment directly obtained from the dielectric constant of the dilute solution using a method of H. KUHN. This method is based on the assumption that a π-electron of a dissolved molecule sees the σ-electrons of the molecule and of the surrounding solvent, a saturated hydrocarbon, as a continuous uniform medium of dielectric constant 2. Thus the π-electron dipole of the solute molecule is regarded as being imbedded in a continuous medium of dielectric constant 2. It was found that the values of the π-electron dipole moments determined by the two methods agree well. Furthermore these experimental values agree with a theoretical value obtained in the case of N- [4-hydroxy-phenyl] -pyridinium-betain II using the one dimensional electron gas method including electron repulsion. The order of magnitude of the π-electron dipole moment of I clearly shows that the ground state of this molecule is highly polar.

A simple kinetic model is presented that describes the frequency-time-behaviour of the fluorescence of molecules showing an anomalous Stokes shift. A discrete and a continuous description of this model are given. Results are compared with an earlier formulation given by Bakhshiev [4]. Vermittels eines einfachen kinetischen Modells wird das Frequenz-Zeit-Verhalten der Fluoreszenz von Molekulen untersucht, deren Fluoreszenzspektrum anomal stark rot verschoben ist. Es wird ein diskretes und kontinuierliches Modell erortert. Die gewonnenen Resultate werden mit einer fruheren Formulierung von Bakhshiev [4] verglichen.

Synthese und spektrale Eigenschaften der Pyridinium-Verbindungen 4b, 4c, 4e (Tab. 1), 8 (Tab. 2) und 9 (Tab. 3) werden beschrieben. Die solvatochromen Pyridinium-N-phenol-betaine 4b und 4e gestatten als sekundare Standardfarbstoffe die Erweiterung einer fruher beschriebenen Losungsmittelpolaritatsreihe auf unpolare Losungsmittel. Das dimere Pyridinium-N-phenol-betain 8 weist wie 4a eine ausgepragte negative Solvatochromie auf. Pyridinium-N-phenol Betaines and their Application for the Characterization of Solvent Polarities,. Extension of the Solvent Polarity Scale by Application of Alkyl-substituted Pyridinium- N-phenol Betaines The syntheses and spectral properties of the pyridinium compounds 4b, 4c, 4e (table 1), 8 (table 2) and 9 (table 3) are described. The solvatochromic pyridinium-N-phenol betaines 4b and 4e as secondary standard dyes permit an extension of a formerly described solvent polarity scale by unpolar solvents. The dimer pyridinium-N-phenolbetaine 8, like 4a, shows a pronounced negative solvatochromism.

A series of 5′-substituted-2′-hydroxy-4-stilbazolium methiodides was prepared by reaction of 5-substituted salicylaldehydes and 4-picoline methiodide. Reaction of these with base leads to the corresponding betaines, which are highly solvatochromic. In addition, 1 : 1 complexes of the methiodide salts and the betaines were isolated from the initial reaction. The energies of the long wavelength transitions of the salts, the betaines and the 1 : 1 complexes of these are directly proportional to the electrophilic substituent constants (σ+) and the slopes are positive. Hence, the transitions appear to involve electron transfer from the salicyl ring to the pyridyl moiety. The solvatochromisms of the betaines and the complexes are directly proportional to the solvent polarity parameter, ET. The slopes are positive, meaning the dipole moments decrease upon excitation, again consistent with the charge transfer transition mentioned above. The relative slopes are rationalized on the basis of substituent effects.

UV./VIS.-, ORD.-, CD.- and fluorescence spectra of the drosopterins are discussed on the basis of the proposed structure 1. The drosopterins show 4 pK-values in the normal pH range and are relatively basic compounds as can be seen from electrofocussing and electrophoresis experiments. Solvatochromic effects are in agreement with the merocyanine character of the pigments. Polarographic studies revealed two twoelectron waves of reduction as expected from the structure.

1.4-Dihetero-butadiene (DHB) wie Glyoxal- oder Diacetyl-bis(imine) und Campherchinonmonoimine bilden Serien stabiler „Molybdan(0)”-Komplexe: DHB-Molybdan-tetracarbonyle A, DHB-Phosphin-molybdan-tricarbonyle B und DHB-Bis(phosphin)-molybdandicarbonyle C. Der Vergleich der Solvatochromie von uber 60 Verbindungen der Reihen B und C mit den Komplexen A ergibt genaue Aussagen uber den Oxydationszustand von Metall und Ligand, die Richtung der farbgebenden elektronischen Anregung und die Bedeutung der π-Ruckbindung bzw. die Grose der π-Resonanzintegrale. Die Minima der Anregungsenergien in den Solvatochromiediagrammen und damit die π-Resonanzintegrale hangen von sterischen Faktoren ab und weisen auf Anderungen der Koordinationsgeometrie bei Campherchinonderivaten hin. Bandenhalbwertsbreiten δn1/2 und deren Losungsmittelabhangigkeit durch-laufen Minima parallel mit den Anregungsenergien. Complex Chemistry of Four-Centre π-Systems, V. The „π-Back Bonding”: Solvatochromie of (1.4-Diheterobutadiene)molybdenum Tri- and Dicarbonyls 1.4-Diheterobutadienes (DHB) such as glyoxal or biacetyl diimines and camphorquinone monoimines form series of stable „molybdenum(0)” complexes: DHB-molybdenum tetracarbonyls A, DHB-phosphinemolybdenum tricarbonyls B, and DHB-bis(phosphine)molybdenum dicarbonyls C. Comparison of the solvatochromism of more than 60 compounds of series B und C with that of complexes A gives precise information about the oxidation state of metal and ligand, the direction of the low energy electronic transition and the importance of π-back bonding or the magnitude of π-resonance integrals. The minimum transition energies in the solvatochromism diagrams and thus the resonance integrals depend on steric factors. Irregularities with camphorquinone derivatives can be understood as changes in coordination geometry. Half widths δn1/2 and their solvent dependance minimize along with transition energies.

1-Benzothiazolyl- and 1-benzoxazolyl-3-methyl(or phenyl)-5-arylformazans are synthesized. The depth of the color of the similarly structured 1-benzazolyl-5-arylformazans depends on the nature of the benzazole group. The power of the chromophores decreases in the following order: 1-alkyl-benzimidazole > benzothiazole > benzoxazole. Unsymmetrical 1-benzazolyl-5-arylformazans exhibit positive solvatochromism.

Die Absorptionsmaxima der Elektronen-Spektren von Acenen lassen sich durch P(2) und/oder M angeben. P(2/1) ist zur mathematischen Darstellung bei den Acenen weniger geeignet. Eine Solvatochromie der Acene, Phene und Starphene ist nachweisbar. Maxima of absorption in electronic spectra of aromatic compounds like the acene-series fit nicely with methods P(2) and M. A correlation by method P(2/1) is relatively ineffective. Solvatochromism exists in trichlorobenzene solutions of acenes, the same is most probable for phenes and starphenes.

The kinetics of aquation of bis(2,2′;6′,2″-terpyridyl)iron(II), [Fe(terpy)2]2+, have been examined in aqueous solution, and a mechanism consistent with the observed pH–rate profile proposed. Activation parameters for fission of the first iron–nitrogen bond have been determined and compared with those for related complexes. The rate law for reaction of [Fe(terpy)2]2+ with cyanide ion is as in equation (i). Activation parameters for the –d[Fe(terpy)22+]/dt=k9+k10[CN–][Fe(terpy)22+](i), k10 path, which is the dominant reaction route, are compared with those for analogous second-order reactions of similar iron(II) complexes with cyanide ion. Solvatochromic behaviour is reported for the [Fe(terpy)(CN)3]– anion, the primary product of the reaction of [Fe(terpy)2]2+ with cyanide.

Samples of Nile blue sulphate (Geigy and G. T. Gurr) were separated by silicic acid thin layer chromatography. The blue sulphated oxazine base was found to consist of 3 components with identical absorption spectra in the visible range. These probably represent isomeric forms of the dye. The red oxazone travelled as a single component. At least 6 minor constituents, present in small amount, were identified. Spectrophotometric examination showed that the sulphated oxazine base has 3 absorption maxima. The absorption spectrum is influenced by pH, dye concentration, dye solvent, and physical state. The absorption spectra of the oxazone and free oxazine base were also measured. These showed marked solvatochromic effects, absorption maxima moving to shorter wavelengths with decreasing solvent polarity.

1.4-Diaza-butadiene-(1.3) bilden mit Kupfer(I)-halogeniden stark farbige, monomere 1:1-Komplexe 2-11, 16-20, 24, 25 mit dreifach koordiniertem Kupfer. Diese Koordination bestimmt das elektronenspektroskopische Verhalten. Wahrend in Diazabutadien-Komplexen anderer Metalle in niedrigen Oxydationsstufen die langstwellige Absorption sehr starken Metall-Ligand-charge-transfer-Charakter hat, fehlt hier bei etwa gleich starker Beteiligung von Metalltermen im Grundzustand und angeregten Zustand die typische Solvatochromie und die extrem hohe Intensitat des farbgebenden Ubergangs. Copper(I)-diazabutadiene Halides 1,4-Diazabuta-1,3-dienes react with cuprous halides to form strongly coloured, monomeric 1:1 adducts 2-11, 16-20, 24, 25, containing copper with threefold coordination. This coordination number determines the spectroscopic behaviour. While diazabutadiene complexes of other metals in low oxidation states show a long-wavelength absorption with strong metal-to-ligand CT character, in the copper complexes 2-11, 16-20, 24, 25 the metal terms are about equally important in the ground and excited state without showing the typical solvatochromism and the extremely high intensity of the chromogenic transition.

The correlation between the absorbance of a merocyanine dye in an organic solvent and the water content of the solvent has been investigated. The merocyanine dyes investigated are 1-methyl-4-[(4-oxocyclohexa-2, 5-dienylidene)-ethylidene]-1,4-dihydropyridine (I), 1-methyl-4-[(2-oxocyclohexa-3,5-dienylidene)-ethylidene]-1, 4-dihydropyridine, 1-methyl-2-[(4-oxocyclohexa-2,5-dienylidene)-ethylidene]-1, 2-di-hydropyridine and 1-methyl-2-[(oxocyclohexa-3,5-dienylidene)-ethyl-idene]-1, 2-dihydropyridine, and the organic solvents are isopropanol, acetone, acetonitrile and pyridine. The possibility of determining a trace amount of water in an organic solvent is demonstrated, and a procedure is proposed for the determination of trace water in pyridine. The sensitivity of the method depends on the solvent, being more sensitive in an aprotic solvent than in a protic one ; for example, 0.05 or 0.27 mg of water in 1 ml of acetonitrile or of isopropanol respectively can be detected with I, by use of an ordinary spectrophotometer.

The syntheses, dipolar electronic structures, and solvent-dependent electronic spectra of square-planar dithiolene α-di-imine nickel complexes are reported.

A series of 1-(2-pyridyl)-3-phenyl-5-arylformazans, which form deeply colored complexes with Zn2+, Cu2+, Co2+, and Ni2+ salts, were obtained by coupling of arenediazonium salts, containing various substituants in the phenyl ring, with benzaldehyde 2-pyridylhydrazone. The presence of a nitro group causes deepening of the color and leads to the appearance of negative solvatochromism.

Solvent effects on the bathochromic shift in the first π–π* band of aminonitropyridines were examined. They were interpreted in terms of inter- and intra-molecular hydrogen bonding, as well as of transition polarizability which determines solvatochromism. All possible dissociation constants of conjugate acids of amino-, diamino-, nitro-, and aminonitro-pyridines have also been measured at 25°C by spectrophotometric determination of acid–base concentration ratios. The influence of amino- and nitro-groups in the pyridine ring on pKa1 and pKa2 was discussed on the basis of electrical characteristics of substituents and electron availability of reaction site.

The solvent power of petroleum solvents is highly dependent upon the percentage of aromatic compounds present in the mixture. In alkyl benzenes, it is dependent upon the proportion of aromatic character in the compounds. Suppliers of petroleum solvents frequently state the aromatic content of their solvents or provide figures for the Kauri-Butanol number, mixed aniline point, or related indicators of solvent power. When these data are not readily available, aromatic content in the petroleum solvents can be estimated by extraction with fuming sulfuric acid (R. L. Feller in Application of Science in the Examination of Works of Art, Museum of Fine Arts, Boston, 1959, p. 51; Feller, Stolow, anWiJnes, On Picture Varnishes and Their Solvents, Intermuseum Conservation Association, Oberlin, 195).