CRANAD-1 as a cyanide sensor in aqueous media: a theoretical studyElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra19045f

The lethal toxicity of cyanide ions to animals and the environment has led to considerable research into the development of methods for rapid and sensitive cyanide detection. CRANAD-1, 2,2-difluoro-4,6-bis[β-(4-hydroxy-3-methoxystyryl)]-1,3,2-dioxaborine has been demonstrated experimentally as a specific sensor for cyanide ion. However, the theoretical explanation for this phenomenon will help us to unfold the mechanism of interaction further. Detailed investigation on the binding energies of CRANAD-1 in presence of various anions such as CN − , F − , Cl − , Br − , AcO − , SCN − and NO 3 − in acetonitrile-water 4 : 1 (v/v) was carried out using B3LYP level of density functional theory using SDD and 6-311++G** as basis sets. The results revealed the H-bond formation of phenolic -OH of CRANAD-1 with cyanide ion, lead to selective sensing of CN − ion with minimum energy. The λ max absorption values calculated from B3LYP/SDD also support experimental reports of selective sensing of CN − compared to other anions with Δ λ max = 85.72 nm and it confirms that the 1 : 2 complex is more stable. The comparison of binding energies of cyanide complexes of 4-hydroxy-3-methoxystyrene and CRANAD-1 reveals better cyanide sensing of Donor-Acceptor-Donor (D-A-D) system, CRANAD-1. The Nuclear Independent Chemical Shift (NICS) calculation confirms the quinonoid structure conversion of phenyl ring and Natural Bond Orbital (NBO) analysis confirms the charge transfer (CT) from CN − to CRANAD-1 is more. The lethal toxicity of cyanide ions to animals and the environment has led to considerable research into the development of methods for rapid and sensitive cyanide detection.