Synthesis and photophysical properties of star-shaped (D-π)3 - A molecules with an n-heteroaromatic core

Star-shaped π -conjugated molecules, which are branched molecules with a general structure consisting of several (more than three) linear π -conjugated chains connected to a central core, are an attractive target. This is because their molecular properties originating from the star- shaped geometric and electronic structures can be different to their linear-shaped π -conjugated analogues. Donor (D)-π -acceptor (A) molecules, which are composed of donor (electron rich) and acceptor (electron deficient) segments connected by a π -spacer, are also an attractive target due to their inherent photophysical properties based on the intramolecular charge transfer (ICT) process from a donor to an acceptor through a π -spacer. Examples of such photophysical properties include a solvent-polarity responsive fluorescence from the highly-polarized ICT excited state (fluorosolvatochromism) and a cation responsive fluorescence of the D-π -A molecule with an amino-donor-type cation receptor based on on-off switching of the ICT process triggered by a cation binding event. Our current efforts have focused on the synthesis and elucidation of the ICT-based photophysical functions of the star-shaped (D-π) 3-A molecules which have a complexed structure of the star-shaped and D-π -A structures. Herein, we report the synthesis and photophysical properties, including fluorosolvatochromic and proton-sensing properties of 2,4,6-tris (5-aryl-2-thienyl)-1,3,5-triazine, -pyrimidine, and -pyridine derivatives, which are designed as the star-shaped (D-π) 3-A molecules consisting of an electron deficient N- heteroaromatic core( A) and three donor aryl terminals( D) linked by a thiophene spacer(π). © 2021 Society of Synthetic Organic Chemistry. All rights reserved.