Acenaphthene-imidazole based chemosensors for selective detection of tin and copper ions and their biological application

Abstract

Two chemosensors derived from acenaphthene-imidazole namely, 4-(2-(7H-acenaphtho[1,2-d]imidazole-8-yl)-4-bromophenoxy)butyl acetate (1) and 4-(1-(7H-acenaphtho[1,2-d]imidazole-8-yl)naphthalen-2-yloxy)butyl acetate (2) were synthesized for the purpose of detecting tin (Sn²⁺) and copper (Cu²⁺) ions. The chemosensors were comprehensively characterized using various spectroscopic techniques, including FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry and single crystal X-ray diffraction analysis. Upon exposure to Sn²⁺ and Cu²⁺ ions in acetonitrile (ACN) solutions, chemosensors 1 and 2 exhibited selective increases in fluorescence intensity at 570 nm and 615 nm, respectively. This behavior was attributed to the chelation-enhanced fluorescence (CHEF) mechanism. The binding constants for the formation of the 1-Sn²⁺ and 2-Cu²⁺ complexes were determined using the modified Benesi–Hildebrand equation to be approximately 1.6 × 10⁴ M⁻¹ and 3.3 × 10⁴ M⁻¹, respectively. The results indicated that the sensors exhibited specific coordination with Sn²⁺ and Cu²⁺ ions. The detection limits for Sn²⁺ and Cu²⁺ ions using sensors 1 and 2 were calculated to be 1.2 × 10⁻⁹ M and 2.1 × 10⁻⁹ M, respectively. Additionally, the sensors were shown to be suitable for live cell imaging, with minimal cytotoxicity, highlighting their potential for cellular detection of Sn²⁺/Cu²⁺ ions.