Determination Of CO2 and SCN' binding capacities of [5, 12-dioxa-7, 14,dimethyl- 1,4,8, 11-tetraazacyclotetradeca-1,8 diene(L)) CO(II) complex

Abstract

Cobalt(II) complex of [5.12-dioxa-7 .14,dimethyl-1 ,4,8, 11-tetraazacyclotetradeca1,8-diene(L)] was synthesised using a template synthesis and characterised using UV visible spectroscopy, cyclic voltammetry (CV) and FT-IR techniques. CO2 trapping capacity was studied with a Vernier CO2 gas sensor capable of measuring the transmitted amount of C02. The solid Co(II) complex shows more CO2 absorption than that of solid starting material. CoCI2.

In UV-visible spectroscopic analysis. the intensity of the orange colour in an aqueous solution of the complex increases with the addition of 0.1 M potassium thiocyanate solution to the metal complex. The intensity of the d-d band at 500 nm decreases while the intensity of CT band around 210 nm increases. This occurs through an isobestic point at 260 nm indicating a SCN' association to the complex and FT-IR data confirm the presence of the desired complex.

Cyclic voltammetric studies of the Co(II) complex shows a reversible band corresponding to the Co(II)/Co(I) redox couple. When the DMSO solution of the complex is saturated with C02. the current intensity of the oxidation peak disappears and that of the reduction peak slightly increases. The reappearance of the original reversible redox band after passing N2 may be indicative of its affinity towards CO2. Reduced Co(I) centre of the complex may coordinate with C02. and the coordinated complex may not be easily oxidised back to the original compound.