Pinacyanol

A dye used in the coloration of materials, such as fibers, must be present as the monomer if it is to adsorb to the material s surface. This experiment describes how spectrophotometry can be used to determine the equilibrium constant between a monomer and a dimer for the dye pinacyanol iodide in water. 

Pinacyanol chioride [2768-90-3] M 388.9, m 270 (dec). Crystd from EtOH/diethyl ether. 

In a study looking at solvent stability [424], various aqueous-miscible solvents (tetrahydrofuran, acetonitrile, isopropanol, methanol, and A,A-dimethylformamide) were used with pinacyanol chloride as substrate. Although a PAH was not used as a substrate, the results may be extrapolated to PAH reactions. The greater impact of peroxide as compared to the solvent on biocatalyst stability was reported in this study and the need to control peroxide concentration was noted. 

Embedding of pinacyanol in a three-dimensional polyphenylene dendrimer results in a red-shift of absorption (from 600 to 620 nm) and emission (from 625 to 648 nm) maxima and in an increase of the quantum yield from 9 x KT4 for free dye in water to 1.4 x 10 2 after insertion in the dendrimeric architecture [71]. This dendrimer was used to develop two FRET systems utilizing cyanine dyes as the donor (DTCI) and the acceptor (pinacyanol and 26a) molecules [72], The FRET system allows the time-resolved detection, where energy transfer can be observed at the single-molecule level. 

Batchelor EK, Gadde S, Kaifer AE (2010) Host-guest control on the formation of pinacyanol chloride H-aggregates in anionic polyelectrolyte solutions. Supramol Chem 22 40-45... 

To estimate how many dye molecules fit into the dendritic micelles, UV-titra-tion experiments have been employed. In comparison with the spectra of a pure pinacyanol chloride solution in water, the peaks of the absorption maxima of the dye in the presence of the dendrimer are shifted bathochromically due to solvatochromic effects, which indicates the incorporation of the dye within the branches of the dendrimer. At dye-to-dendrimer molar ratios higher than 4 1, in addition to the bathochromic shifts, hypsochromically shifted peaks start to appear, indicating that the dendrimer is not incorporating further dyes. We interpret this as an incorporation of up to four dyes within the branches of the dendrimer. This observation correlates with the calculated available space within the dendrimer, obtained from the molecular simulations. Further studies of the interactions of the dyes within the dendritic micelle are in progress. 

Figure9.8 The absorbance of 1.05 x 10 M pinacyanol chloride at 610.0 min pH 9.59 sodium borate buffer (I = 0.1) at 50 °C vs. dodecanoate concentration. The absorption spectrum of pinacyanol chloride in aqueous solution of anionic soaps changes sharply to one characteristic of its solutions in organic solvents within a small range of soap concentration (X ax 610 nm). This effect is attributed to the formation of micelles, in whose hydrocarbon-like layers or cores the dye is solubilized. The concentration of soap at which this spectral change occurs is taken as the cmc. The use of dyes for the determination of cmc values may lead to micelle formation at a concentration below the true cmc. In practice, the method gives only a rough approximation of the cmc. (Adapted, with some modifications, from Corrin et al., 1946.)...

Corrin, M. L Klevens, H. B and Harkins, D. (1946). The determination of critical concentrations for the formation of soap micelles by the spectral behavior of pinacyanol chloride. J. Chem. Phys., 14,480-6. 

Closely related are the cyanine dyes, for example cyanine (62) itself, which is formed from the ethiodide salts of lepidine and 4-iodoquinoline in the presence of base (Scheme 51). Analogous monomethine cyanines can have the quinoline nuclei linked 2,2 (pseudocyanines) and 2,4 (isocyanines). Quinaldine ethiodide on condensation With ethyl orthoformate gives the 2,2 -linked trimethine cyanine (carbocyanine) (63), known as pinacyanol (Scheme 51). 

The photoconductive gain G as measured from saturated current-voltage curves is of the order of unity in several dyes 3,50,51) .g. in malachite green G =0.2, pinacyanol G=0.37 and merocyanine A 10 7 G=0.6. 

Influence of Dielectric Constant on the Spectral Behavior of Pinacyanol 171... 

Fig. 11. Sensitized photoconductivity (/) and absorption (2) spectra of PVC with pinacyanol [59]...

Fig. 11. Kinetic energy distribution of photoelectrons (a) from a Pinacyanol layer, (6) from a Pinakryptol layer. The curves... 

The kinetic spectrum reveals more peculiar details than the usual spectral efficiency curve of the external photoeffect. For example, the kinetic spectra for pinakryptol and pinacyanol are quite different, whereas the efficiency curves are much alike.45... 

Another interesting class of molecules are stilbene derivatives with charge donating groups. These compounds offer the opportunity to explore the role of polar solvation dynamics (dielectric friction) in cis/trans isomerization. Interesting papers on this subject have been published by Waldeck et al. [145] and Rulliere et al. [146]. Other well-studied polar excited state isomerization examples include pinacyanol, l,l -diethyl-4,4 -cyanine, and crystal violet, which have been studied by Sundstrom, Gilbro and their coworkers [148] and Ben-Amotz and Harris [148] and others who are referenced in these papers [148,149],... 

Even more important was pinacyanol [605-91-4] (48), which was obtained from quaternary quinaldine by reaction with formaldehyde to form the leuco compound and atmospheric oxidation in an alkaline medium [109],... 

The unimolecular micellar characteristics of this poly(ammonium carboxylate) 156 were demonstrated 179 by UV analysis of guest molecules, such as pinacyanol chloride, phenol blue, and naphthalene combined with fluorescence lifetime decay experiments employing diphenylhexatriene as a molecular probe. The monodispersity, or absence of intermolecular aggregation, and molecular size were determined by electron microscopy. 

The sensitization effect is not limited to the above mentioned dyes. For example, Terrel98 studied charge carrier generation and injection processes in the crystal violet/PVK system. Meier et al.124 extended the spectral response of PVK to over 600 nm by pinacyanol. Okamoto et al.12s sensitized PVK into the visible region by Malachite Green, etc. 

An essay on her pinacyanol work gained her the Gamble Prize in 1921, and that same year she was awarded the Yarrow Scientific Research Fellowship to continue her work in Cambridge, where she remained until 1924. She worked for a few months at the Davy Faraday Research Laboratory of the Royal Institution, and then was hired by the photographic company of Ilford Ltd.00 The 6 years she spent at Ilford were marred by difficult relations with the Research Director, Frank Forster Renwick. Matters came to a head in 1930, when Hamer complained that her new laboratory was so hot in summer it was impossible to work Renwick refused to take any action and Hamer resigned. 

---