Synthesis and Crystal Structure of a Heterotrimetallic 12-Metallacrown-4 with 5-Nitrosalicylhydroxamic Acid

Abstract

A heterotrimetallic aluminum-dysprosium-sodium 12-MC-4 complex, Dy^IIINa(ben)₄[12-MC_{Al(III)N(5−nitroshi)}-4](H₂O)_3.58(DMF)_2.44·7.86DMF·0.28H₂O (1), where DMF is N,N-dimethylformamide, with the metallacrown (MC) framework ligand 5-nitrosalicylhydroximate (5-nitroshi³⁻) and the ancillary bridging ligand benzoate (ben⁻) has been synthesized and characterized by FT-IR and single-crystal X-ray diffraction. The MC framework ligand 5-H₃nitroshi is a derivative of the common MC ligand salicylhydroxamic acid (H₃shi), and this is the first instance of 5-H₃nitroshi being used for a metallacrown. The MC ring consists of four Al^III ions, and the MC binds one Dy^III ion on the convex side of the central cavity. Four benzoate anions tether the Dy^III ion to the MC cavity by forming a bridge between each ring Al^III ion and the central Dy^III ion. The position of the Na⁺ ion is unique regarding this class of 12-MC-4 complexes as the sodium ion is disordered over four binding sites on the MC. The main occupancy [0.326(3)] of the sodium ion is located on the concave side of the MC central cavity, opposite of the Dy^III ion. This location is typical for this class of 12-MC-4 molecules. The other three binding sites occur of the periphery of the molecule, and the sodium ion binds to phenolate and carbonyl oxygen atoms of the 5-nitroshi³⁻ MC framework ligands. The coordination environments of each sodium ion are completed by a mixture of water and DMF solvent molecules. The total occupancy of the sodium ion sites is unity.

AbstractSection Graphical Abstract

The heterotrimetallic Dy^IIINa(ben)₄[12-MC_{Al(III)N(5-nitroshi)}-4] complex is constructed with the metallacrown framework ligand 5-nitrosalicylhydroxamic acid (5-H₃nitroshi). The sodium cation is disordered over four different binding sites