Substituent Modulation of Structures, Luminescence, and TNP Sensing Abilities for Coordination Polymers

Abstract

The modulation of coordination polymers (CPs) with specific structures and functions is greatly challenging. This work explores the function of the substituent in the modulation of structures, luminescence, and sensing abilities for CPs. Compared with 4,4′-((9H-fluoren-9-ylidene)-methylene)dipyridine (L-2), a new aggregate-induced emission (AIE) molecule 4,4′-((2,7-di-tertbutyl-9H-fluoren-9-ylidene)-methylene)dipyridine (L-1) with two tert-butyl substituents was successfully synthesized. L-1 and L-2 were developed as functional ligands to construct two distinct one-dimensional (1-D) double-chain CPs [Cd(L-1)(2,5-TDC)(H 2 O)] n (1) and [Cd(L-2)(2,5-TDC)(H 2 O)] n (2) through very similar synthetic routes. 1 is fabricated by L-1 linking with two 2,5-TDC-Cd single chains to form a double-chain architecture. Meanwhile, 2 has a 2,5-TDC-Cd double-chain skeleton with L-2 terminal ligands. 1 and 2 have good water and thermal stabilities but show different luminescent properties. Compared with 1, 2 has an obviously enhanced TNP sensing ability. The quenching constant (4.5 × 10 4 M −1) of 2 toward TNP is nearly three times higher than that (1.55 × 10 4 M −1 ) of 1. The TNP detection limit (5.27 × 10 −4 mM) of 2 is about 1 order of magnitude lower than that (4.67 × 10 −3 mM) of 1. The mechanism of distinct sensing performance for 1 and 2 toward the TNP is explored in detail.