Sigma-spacer regulated thiophenyl triazine conjugates: synthesis and crystal, electronic and luminescent properties

A water-accelerated Pd catalyzed Suzuki-Miyaura cross-coupling reaction was developed for the synthesis of thiophenyl triazine conjugates (TTCs). The compounds (2a-2e and 3a-3e) with five sigma-spacers were obtained and fully characterized. The X-ray analysis of 2a, 2d, and 3d found that the length of the intermolecular H bond was 3.465(3) angstrom and the pi-pi interactions ranged from 3.6538(2)-3.9519(1) angstrom. Five sigma-spacers of TTCs had an effect on their emissions from blue (363 nm) to yellow (530 nm) whilst 2- and 3-thiophenyl chromophores finely tune the emission from 530 to 504 nm. The DFT computation showed the TTCs had low HOMO (-6.8 eV) and LUMO (-2.5 eV) energy and high triplet energy (E-T, 2.4 eV). The energy level and gap of TTCs were regularly modulated by the sigma-spacer.