Nonsymmetric Benzo[<i>a</i>]fused and Thiophene/Thieno[3,2-<i>b</i>]thiophene[<i>b</i>]fused BODIPYs: Synthesis and Photophysical Properties

Abstract

The fusion of sufficient-electron heterocycle rings into the[<i>a</i>]/[<i>b</i>]-position of the BODIPY core would result in a large redshift wavelength, thus achieving red or near infrared emission. In this paper, we described the synthesis of nonsymmetric benzo[<i>a</i>]fused and thiophene/thieno[3,2-<i>b</i>]thiophene[<i>b</i>]fused BODIPY derivatives <b>2-3</b> while containing a reactive site, and then, <b>4-7</b> were developed by nucleophilic substitution reactions of <b>3</b> with various nucleophilic agents in high yields. X-ray crystallographic analysis of <b>2-7</b> revealed that the core structure adopted a planar geometry and π-π interactions were observed in the packing structure. BODIPYs <b>4</b> and <b>6-7</b> displayed a hypochromic shift in the absorption and bathochromic shift in the emission with increasing solvent polarity because of the formation of resonance structures resulting from the change of the C-N distance, which was rationalized by density functional theory (DFT)/time-dependent-DFT calculations.