Theoretical study of the structure and water affinity of [M(18C6)(HFA)2] complexes for M = Zn, Cu, Hg, Co, Ni, and Pt

The structures of the [M(18C6)](2+) cations, where M = Zn, Cu, Hg, Ni, Co, and Pt, and cis- and trans-[M(18C6)(HFA)(2)]/[M(18C6)(NO3)(2)] molecules in the gas phase have been calculated by the density functional theory method in the B3LYP/6-31G*//6-311++G** + LanL2Dz approximation. Geometry optimization has been performed, and the strength of binding of the central cation to the crown ether (18C6) and the degree of structural similarity of the [M(18C6)(HFA)(2)] compounds for different central atoms M have been evaluated. For all [M(18C6)(NO3)(2)]/[M(18C6)(HFA)(2)] molecules (M = Zn, Cu, Hg, Ni, Co, Pt), the vertical ionization potential and the vertical electron affinity have been calculated. These parameters are of interest for analysis of the stability of volatile compounds [M(18C6)(HFA)(2)] to donor-acceptor interactions with other components of the gas phase, for example, with water vapor, which is usually a Lewis base with respect to the systems in question and can donate electron density in the course of complexation with the central atom. The propensity of the [M(18C6)(NO3)(2)]/[M(18C6)(HFA)(2)] molecules to react with water is considered for a wider range of metals M2+ = Ba2+, Sr2+, Pb2+, Mn2+, Cd2+, Zn2+, Cu2+, Hg2+, Co2+, Ni2+, and Pt2+, with taking into account the degree of matching between the ionic radii of M2+ cations and the 18C6 cavity size.