Optical properties of 2,3-diaza-1,3-butadiene bridged oligothiophenes: A combined experimental and theoretical study

The syntheses, spectral measurements and the AM1 (Austin model 1) geometry optimisation of N,N′-bis-thiophen-2-ylmethylene-hydrazine (IIIa), N,N′-bis-(3-methyl-thiophen-2-ylmethylene)-hydrazine (IIIb), N-[2,2′]-bithiophen-5-ylmethylene-N′-thiophen-2-ylmethylene-hydrazine (IIIc), N,N′-bis-[2,2′]-bithiophen-5-ylmethylene-hydrazine (IIId), N-[2,2′; 5′,2″]-terthiophen-5-ylmethylene-N′-thiophene-2-ylmethylene-hydrazine (IIIe), N-[2,2′]-bithiophen-5-ylmethylene-N′-[2,2′; 5′,2″]-terthiophen-5-ylmethylene-hydrazine (IIIf) and N,N′-bis-[2,2′; 5′,2″]-terthiophen-5-ylmethylene-hydrazine (IIIg) are elaborated. The electron absorption spectra for all-trans conformers are obtained by ZINDO/S method and compared with the experimental data. The influence of the chain length on the electronic polarisability and second-order hyperpolarisability is investigated using the time-dependent Hartree–Fock method in AM1 approach.