—Direct photooxidation of cyanine dyes was found to be markedly enhanced by formation of hypsochromically shifted (H) aggregates. Singlet oxygen was found to attack many cyanines possessing low oxidation potentials with rate constants in excess of 108 t mol-1 s-1. Singlet oxygen attack on 3,3′-diethyl-8,10-dimethylthiacarbocyanine yields carbonyl products consistent with 1,2 addition to the 2,8 bond of the methine chain.

Direct and sensitized photooxidation of cyanine dyes.

The formation of complexes between electron donors and acceptors has long been recognized a s an important phenomenon. Many of themolecular complexes are colored and give rise to new absorption bands in the electronic spectra. These molecular complexes have been investigated by employing a variety of physical methods such as optical spectroscopy, magnetic resonance spectroscopy, calorimetry, dielectric measurements, and X-ray diffraction. Studies of donor-acceptor complexes are of value in understanding various types of reaction mechanisms, including molecular phenomena in biological systems. Some of the relatively recent developments in the study of molecular complexes are: the classification of donors and acceptors by Mulliken [l], vibrational spectroscopy, particularly in the very-low-frequency region [2,3], estimation of the per cent charge transfer by dipole moment measurements [4–6], studies of weak interactions (contact pairs) [7], spectra and thermodynamics of complexes in vapor phase [8,...

Spectroscopy of electron donor-acceptor systems

Styryl dyes 4a-e containing a 15-crown-5 ether unit and a quinoline residue with a sulfonatoalkyl or sulfonatobenzyl N-substituent were synthesized. The relationship between the photochemical behavior of these dyes and their aggregates derived from complexation with Mg(2+) in MeCN was studied using (1)H NMR and absorption spectroscopy. The E-isomers of 4a-e were shown to form highly stable dimeric (2:2) complexes with Mg(2+). Upon irradiation with visible light, the dimeric complexes undergo two competing photoreactions, viz., geometric E --> Z isomerization, resulting in an anion-capped 1:1 complex of the Z-isomer with Mg(2+) and stereospecific syn-head-to-tail [2+2]-cycloaddition, affording a single isomer of bis-crown-containing cyclobutane. The N-substituent in the dye has a dramatic effect on the photochemical behavior of the dimeric complex. Molecular dynamics and semiempirical quantum-chemical calculations were carried out to interpret the observed photocycloaddition in the dimer. Conformational equilibria for the dimer of (E)-4b were analyzed using (1)H NMR spectroscopy.

Novel photoswitchable receptors: synthesis and cation-induced self-assembly into dimeric complexes leading to stereospecific [2+2]-photocycloaddition of styryl dyes containing a 15-crown-5 ether unit.

The renal secretion of organic cations (OCs) involves a carrier-mediated exchange of OC for H+ in the luminal membrane of proximal cells. To assess the influence of chemical structure on the interaction of potential substrates with this process we examined the effect of a series of quaternary ammonium compounds on the transport of the OC tetraethylammonium (TEA) in a preparation of isolated renal brush-border membrane vesicles. Apparent inhibitory potency varied over a factor of 104, as expressed in inhibitor coefficients (KiTEA) whose approximate values ranged from 0.5 μM to 5 mM. The poorest inhibitors of TEA/H+ exchange were those molecules with carboxyl or hydroxyl residues, whereas the addition of methylene groups to a parent molecule tended to increase inhibitory potency. A plot of apparent KiTEA versus calculated octanol:water partition coefficient (expressed in terms of a relative lipophilicity factor) showed a clear correlation between these two parameters, although there was considerable variability between apparent lipophilicity and KiTEA for molecules with very different parent structures. For select groups of molecules with similar parent structures (e.g., the n-tetraalkylammoniums or the 4-phenylpyridinium, 3-phenylpyridinium, and quinolinium compounds) the correlation between calculated lipophilicity and apparent KiTEA was more marked. However, even within these groups of closely related parent structures, there appeared to be subtle, but systematic, variations in inhibitory potency that may have been related to the influence of steric factors on the binding of inhibitors to the TEA/H+ exchanger. We conclude that the lipophilic nature of a quaternary ammonium compound represents the predominant factor in the binding to, and subsequent inhibition of, luminal TEA/H+ exchange. Specific steric factors may influence the binding of substrate to the exchanger, but play a secondary role in this interaction.

Structure and interaction of inhibitors with the TEA/H+ exchanger of rabbit renal brush border membranes

The resonance Raman spectra of a series of cyanine dyes, with various lengths of the methine chain, have been obtained. This series consists of the 1,1′-diethyl-2,2′-quino group basic structure. Raman spectra of some dyes with closely related structures were also measured. The Raman bands are assigned to normal modes arising from particular molecular moieties. For comparison purposes, the IR spectra of these dyes are also presented.

The resonance Raman spectra of some cyanine dyes

Synthesis of Some Heterocyclic Quaternary Amine Iodides.

A detailed study of the visible spectra in solution and the infrared spectra of the dyes in the solid state have been made for the following vinylogous series of cyanine dyes: [2-bis (3-ethylthiazolinyl)] cyanine iodides, I; [2-bis (3-ethyl-4-methylthiazolyl)] cyanine iodides, II; and [2-bis (3-ethyl-4,5-diphenylthiozolyl] cyanine iodides, III. Each dye, to be acceptable for study, had to be chromatographically pure, give a correct microchemical elemental analysis, and be free of electron-spin resonance (free radical) signals. These vinylogous series of dyes from a systematic group. That is, in series I there is only a resonant conjugated chain of alternate single and double bonds present between the two nitrogen atoms; in series II there are additional olefinic unsaturated bonds which are in conjugation with the resonant conjugated chain; and in series III there are additional phenyl rings in conjugation with the entire pi bond system present in II. The characteristic red shift of the principal absorption maxima was observed for these dyes in the visible as the number of methine linkages increased. Furthermore, a small relative red shift of the absorption maxima has been observed for this group of dyes and has been interpreted on the basis of the type of unsaturation present in conjugation with the resonant conjugated chain. Assignments of vibrational modes to separate absorption regions have been made for these vinylogous series of dyes. A correlation of the dye structure with the absorption bands has been made. Each vinylog gave rise to a characteristic pattern of resonant conjugated stretching modes in the region 1600 to 1400 cm−1. These modes exhibited a low frequency shift as the resonant conjugated chain-length increased. For a constant number of polymethine linkages these modes are a function of the type of unsaturation present which is in conjugation with the resonant conjugated chain.

Investigation of Spectral Sensitization III. A Study of the Visible and Infrared Spectra of Some Very Pure Bis-Thiazolinyl and Bis-Thiazolyl Cyanine Iodides

Synthesis of Very Pure Cyanine Dyes. Preparation of Vinylogous Series of Bis-Thiazolyl, Bis-Thiazolinyl, Bis-Benzothiazolyl, and Bis-Benzoselenazolyl Cyanine lodides.

A study of the intra-red spectra of cyanine and merocyanine dye intermediates—some heterocyclic quaternary amine iodides

A detailed study of the visible spectra in solution and the infrared spectra in the solid state have been made for the following vinylogous series of dyes: [2-bis(3-ethylbenzothiazolyl)] cyanine iodides and [2-bis 3-ethylbenzoselenazolyl)] cyanine iodides. Each dye, to be acceptable for study, had to be chromatographically pure, give a correct microchemical elemental analysis, and be free of electron-spin resonance (free radical) signals. The characteristic red shift of the principal absorption maxima was observed for these dyes in the visible as the number of methine linkages increased. Assignments of vibrational modes to separate absorption regions have been made for these vinylogous series of dyes. Each vinylog has a characteristic pattern of resonant-conjugated stretching modes in the region 1600–1400 cm−1. These modes exhibit a low-frequency shift as the resonant-conjugated chain length increases. There are bands absorbing in the regions 1594–1572 cm−1 and 1470–1453 cm−1 which are present in all the vinylogs and which have been assigned to the aromatic stretching vibrations of the fused phenyl rings present in all these dyes. There is a band appearing in the region 1000–900 cm−1 which changes systematically with an increase in the number of hydrogens on the bridge and with substitution on the bridge. This band has been assigned to the out-of-plane bending vibrations of the hydrogens in a trans configuration on the bridge. No evidence of a cis isomer was observed in the spectra. There is a band near 760 cm−1 which is split into a doublet and has been assigned to the aromatic CH out-of-plane bending vibrations of the four adjacent hydrogens on the fused phenyl rings. This splitting has been attributed to a crystal field effect which gives rise to in-phase and out-of-phase vibrations of the same groups in two different molecules.

Investigation of Spectral Sensitization IV. A Study of Visible and Infrared Spectra of Some Very Pure Bis—Benzothiazolyl and Bis—Benzoselenazolyl Cyanine Iodides

A. Leifer

Papers

Synthesis of Some Heterocyclic Quaternary Amine Iodides.

Investigation of Spectral Sensitization III. A Study of the Visible and Infrared Spectra of Some Very Pure Bis-Thiazolinyl and Bis-Thiazolyl Cyanine Iodides

Synthesis of Very Pure Cyanine Dyes. Preparation of Vinylogous Series of Bis-Thiazolyl, Bis-Thiazolinyl, Bis-Benzothiazolyl, and Bis-Benzoselenazolyl Cyanine lodides.

A study of the intra-red spectra of cyanine and merocyanine dye intermediates—some heterocyclic quaternary amine iodides

Investigation of Spectral Sensitization IV. A Study of Visible and Infrared Spectra of Some Very Pure Bis—Benzothiazolyl and Bis—Benzoselenazolyl Cyanine Iodides