Conjugated polynitriles

As briefly alluded to, there are different classes of redox-active ligands in addition to the above mentioned ones. For example, we have seen in Chapter 5, Section 8, that azo-groups (in particular, 2-(phenylazo)pyr-imidine) are able to undergo two separate one-electron reduction processes. Conjugated polynitriles (mnt, tcne, tcnq) also constitute an important class of redox-active molecules and the electrochemical behaviour of their metal complexes has been reviewed.107 The same holds as far as alkyldithiocarbamates (Rdtc) and their metal complexes are concerned,108 or nitrosyl complexes in their possible NO+[NO fNO redox sequence.109 Thus, we would like to conclude the present Chapter by discussing a few less known redox non-innocent ligands. 

Conjugated Polynitriles A Novel Class of NLO and Electrical Functional Polymers... 

The temporal evolution of the OKE signals in solutions and films of the linear conjugated polynitriles with different m values was observed. As an example, the time-resolved transient optical Kerr signals of PBN with m = 11.8 are presented (Fig. 24). The signal profiles of all samples are approximately symmetric with respect to the delay time, which indicates a primarily pulse width-limited response. To obtain the relaxation time of the Kerr medium we can fit the experimental curve with an exponential function [45,57]. Because the time constants of all samples are all less than the pulse duration, we can only roughly determine that the relaxation time of all samples is shorter than the laser pulse width (165 fs). The ultrafast optical response may be caused by distortion of the ir-electron cloud occurring with the nonresonant excitation [58]. 

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