Leucocyanides

De Gaouck and LeFevre (25) also studied the conductivity of alcoholic solutions of Malachite Green leucocyanide and Brilliant Green leucocyanide. They found a definite reversibility for the conductance data with alternate irradiation and dark periods only after the first irradiation. Typical resistance for the photochromic dye systems are shown in Figure... 

Leucocyanides as radiation dosimeters Nuclear-substituted triarylrnethane derivatives Amino triphenylacetonitrile... 

Photochemical preparation of stable dyes by irradiation of aminotriarylacetonitriles Photosensitive leucocyanide compositions Photoactivation of leucocyanides Solid photosensitive compositions Purification of triarylrnethane leucocyanides Fuchsine cyanide... 

The photolysis of the leucocyanides of the triphenyl methane dyes in polar solvents proceeds to ionic products, viz. 

Polyacrylamide gels containing a small amount of triphenylmethane leucohydroxide or leucocyanide groups 21) were prepared by free radical copolymerization of di(iV,iV-dimethylaniline)-4-vinylphenylmethane leucohydroxide 12, X=OH, R=... 

CH=CH2) or leucocyanide 12, X=CN, R=CH=CH2) in dimethylsulfoxide in the presence of iV,iV-methylene-hisacrylamide. The gek were swollen to equilibrium by allowing them to stand in water overnight. Then the changes in their weight and dimensions induced by ultraviolet light were measured. 

Fig. 18. Photostimulated dilation and contraction of polyacrylamide gel containing 1.9 mole % pendant triphenylmethane leucocyanide groups with light of wavelength longer than 270 nm at 25 °C [43]. Wo is the weight before photoirradiation...

Fig. 19a, b. Photostimulated (a) color change and (b) dimension change of polyaotylamide gel containing 1.9 mole % triphenylmethane leucocyanide groups in water [43]. Ig is the initial diameter of the disk-shaped gel befOTe photoirradiation... 

The polyacrylamide gel described abobe is the first example showing a reversible deformation of more than 100%. The effect is purely photochemical and reversible. However, this gel has a serious disadvatage in that the response time is slow. To improve this point the effect of electric field on the gel deformation was examined [44]. A rod-shaped polyacrylamide gel containing triphenylmethane leucocyanide groups (25 mm in length and 2 mm in section diameter) was prepared in a capillary tube. The gel rod was inserted between two parallel platinum electrodes in a small... 

Fig. 20. Photostimulated vibrational motion of a rod shaped polyacrylamide gel having 3.1 mol% triphenylmethane leucocyanide groups under an alternating electric field ( + 0.8 v/cm, 0.5 Hz) in water in the preseiK of4x lO MNaCl...

Fig. 26. Photo-effects on water permeation through a porous poly(vinj4 alcohol) gel with tri dmiyl-methane leucocyanide groups (content, 1.9 mol %). ( ) an unmodified membrane ( ) a coated membrane in the dark (O) a coated membraw under UV irradiation...

Absorption and fluorescence spectra of 7-aminocoumarin derivatives have been recorded and the photophysics of coumarin inclusion complexes with 0- and y-cyclodextrins investigated. Solvent effects on the photophysical behaviour of pyrrolocoumarin derivatives are similar to those on the psorolens . Vibronic exciton bands and the absorption spectra of Eosin Y dimers have been analysed theoretically and compared with experimental data. Picosecond spectroscopic studies have been made on the ionic photodissociation dynamics of malachite green leucocyanide . The lowest state produces ions within 0.1 to 0.5 ns whilst for higher states 6-13 ps are sufficient for the development of charge separation. The photophysics of crystal violet in a series of n-... 

Figure 4. Photostimulated size and shape changes of polyacrylamide gels having triphenylmethane leucocyanide groups (3.1 mole %) (A) before photoirradiation, (B) the whole gel being irradiated with ultraviolet light, (C)before photoirradiation, (D) upper side of the rod shaped gel being irradiated.

X 19 X 15 mm) with two parallel platinum electrodes(26). The rod-shaped gel was placed parallel to the electrodes to avoid the contact of the gels with the electrodes. The acrylamide gels containing triphenylmethane leucocyanide groups(25 mm in length and 2 mm in section diameter) were prepared in capillary tubes by the same method as described in the previous section. 

Figure 6. Photostimulated bending motion of a rod shaped acrylamide gel (25 mm in length and 2 mm in section diameter) having 3.1 mole% triphenylmethane leucocyanide groups in an electric field (10 V/cm) in water (A) before photoirradiation, (B)under ultraviolet irradiation, (C) under ultraviolet irradiation, polarity of the electric field being opposite to that in (B).

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