Synthesis and Characterization of Thiophene and Thiazole Containing Polymers

Impact of Preferential π-Binding in Catalyst-Transfer Polycondensation of Thiazole Derivatives

Polymerizing electron-deficient arenes in a controlled, chain-growth fashion remains a significant challenge despite a decade of research on catalyst-transfer polycondensation. The prevailing hypothesis is that the chain-growth mechanism stalls at a strongly associated metal-polymer π-complex, preventing catalyst turnover. To evaluate this hypothesis, we performed mechanistic studies using thiazole derivatives and identified approaches to improve their chain-growth polymerization. These studies revealed a surprisingly high barrier for chain-walking toward the reactive C-X bond. In addition, a competitive pathway involving chain-transfer to monomer was identified. This pathway is facilitated by ancillary ligand dissociation and N-coordination to the incoming monomer. We found that this chain-transfer pathway can be attenuated by using a rigid ancillary ligand, leading to an improved polymerization. Combined, these studies provide mechanistic insight into the challenges associated with electron-deficient monomers as well as ways to improve their living, chain-growth polymerization. Our mechanistic studies also revealed an unexpected radical anion-mediated oligomerization in the absence of catalyst, as well as a surprising oxidative addition into the thiazole C-S bond in a model system.

Vibrational spectroscopic, NMR parameters and electronic properties of three 3-phenylthiophene derivatives via density functional theory

Quantum chemistry calculations have been performed to compute the optimized geometries, vibrational frequencies, and Mulliken Charges at B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) levels for 3-(4-fluorophenyl)thiophene (FPT), 3-(4-nitrophenyl)thiophene (NPT) and 3-(4-cyanophenyl) thiophene (CPT) in the ground state. In addition, the ¹³C and ¹H NMR are calculated by B3LYP/6-311++G(d,p) and B3LYP/6-311++G(2d,2p) methods. The singlet electronic excited state properties of the three compounds were investigated using the time-dependent density functional method (TD-DFT) at the B3LYP/6-311++G(d,p)//TD- B3LYP/6-311++G(d,p) level of theory. The influence of the substituted groups on C9 atom is discussed.