Crystal, molecular and electronic structure of N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)-(1,1'-biphenyl)-4,4'-diamine and the corresponding radical cation.

Oxidation of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD, 1 a) and N,N'-diphenyl-N,N'-bis(2,4-dimethylphenyl)-(1,1'-biphenyl)-4,4'-diamine (1 b) with SbCl(5) affords the corresponding radical cations quantitatively. The crystal and molecular structure of 1 b and [1 b]SbCl(6), the first tetraphenyl benzidene derivatives to be characterised crystallographically in both the neutral and radical cation states, reveal molecular parameters in agreement with the predictions made on the basis of DFT studies. Analysis of the NIR transition in the radical cations [1](+) (.) allows an estimate of the electronic coupling parameter V (1 a(+) (.) 3200 cm(-1); 1 b(+) (.) 3300 cm(-1)), the reorganisation energy lambda(1 a(+) (.) 7500 cm(-1); 1 b(+) (.) 7800 cm(-1)), and the linear coupling constant l (1 a(+) (.) 3100 cm(-1); 1 b(+) (.) 2700 cm(-1)) of the symmetric mode.

SERRS dyes. Part I. Synthesis of benzotriazole monoazo dyes as model analytes for surface enhanced resonance Raman scattering.

The synthesis of seven monoazo benzotriazole dyes for use in surface enhanced resonance Raman scattering, SERRS, is reported. The dyes are all capable of complexing to the silver surface used to provide the surface enhancement found in SERRS and hence act as 'model' analytes. One dye was examined in detail and showed a quantitative relationship between concentration and signal intensity.