A Macrocyclic Chromium(III) complex with mixed Hydroxo and Carbonato bridges: Crystal structure and Magnetic properties of [(tacn)Cr(μ-OH)₂ (μ-CO₃)Cr(tacn)](ClO₄)₂·3H₂O (tacn=1,4,7-Triazacyclononane)

Abstract

A novel homodinuclear complex [(tacn)Cr(μ-OH)₂(μ-CO₃)Cr(tacn)](ClO₄)₂·3H₂O (tacn = 1,4,7-triazacyclononane) has been synthesized and characterized by single-crystal X-ray diffraction analysis. The complex crystallizes in space group Pnma, with a = 14.323(2), b = 21.958(3), c = 9.0092(14) Å, Z = 4, R ₁ = 0.0552, wR ₂ = 0.1222. The structure consists of the binuclear cation [(tacn)Cr(μ-OH)₂(μ-CO₃)Cr(tacn)]²⁺, uncoordinated perchlorate anions and lattice water molecules. Metal centres are linked together by two hydroxo bridges and one carbonato bridge and there are intramolecular Cr–Cr interactions. The geometry around each chromium(III) ion is distorted octahedral. Hydrogen atoms of two neighbouring 1,4,7-triazacyclononane ligands connect with the uncoordinated oxygen atom of the carbonato group through hydrogen bonds to form a 1-D chain. Measurements of variable-temperature (2–300 K) magnetic susceptibilities show an antiferromagnetic interaction between Cr(III) ions.

Keywords:

• Chromium(III) complex
• 1,4,7-Triazacyclononane
• Crystal structure
• Magnetic properties

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. 90101028, 50173011) and the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, P.R.C.

Supplementary Material

Additional material, consisting of atomic coordinates and equivalent isotropic displacement parameters, is available from CCDC, deposit number 188069. Copies of the data can be obtained free of charge on application to the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK (fax: [phone]; E-mail: [email protected]).