Polyamino‐Substituted 1‐Oxa‐3,5‐diazahexatrienes and 1‐Oxa‐3,5,7‐triazaoctatetraenes ( N ‐Acyl‐oligocyanamides): Synthesis, Structures, Cyclovoltammetry and NLO Properties − Experiment and Theory

A homologous series of N ‐acylcyanamides of the formula R 2 N−[C(NMe 2 )=N] n −C(NMe 2 )=O with n = 1−3 has been prepared among similar amino‐substituted N ‐acyl‐oligonitriles by treatment of guanidine 4 with carbamoyl chloride 5 yielding compound 6 ( n = 1) and by ring opening of 1,3,5‐oxadiazinium salts 7 with morpholine ( 8) to give compounds 9 ( n = 2) or with guanidine 4 to give compounds 10 ( n = 3). The all‐dimethylamino‐substituted compound 10d reacts with ZnCl 2 to yield a six‐membered chelate complex 10d · ZnCl 2 . The molecular structures of 9e,f, 10a − d and 10d · ZnCl 2 have been elucidated by X‐ray crystallography and partly by DFT calculations. They deviate strongly from planarity with some examples showing helical structures. From the calculations, 10d is predicted to be a rather strong neutral base. One or two oxidation peaks, depending on the chain length, were observed by cyclic voltammetry. For the most extended derivative 10d a first oxidation potential of 1.12 V was measured. The molecular first hyperpolarizablities β 0 were determined by hyper‐Rayleigh scattering (HRS) measurements. The β 0 values increase with chain length and reach 5×10 −30 esu for the longest derivative 10d . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)