Copper(II) bis-chelate paddle wheel complex and its bipyridine/phenanthroline adducts

Abstract

Bola-shaped diester dicarboxylic acid 2-({2-[(2-carboxybenzoyl)-xy]ethoxy}carbonyl)benzoic acid (L¹H₂) was synthesized by desymmetrizing phthalic anhydride using 1,2-ethane diol. The corresponding dinuclear copper(II)-tetracarboxylate complex [Cu₂(L¹)₂·(DMF)₂] (1) has been synthesized. This paddle wheel complex was self-assembled with [15]-membered bis-chelate ring on either sides of the M–M axis. Upon treating with phenanthroline/bipyridine, the symmetrically formed bis-chelate rings in 1 were selectively desymmetrized into monochelate rings. The dinuclear association in 1 rearranged into mononuclear in [Cu(L¹)·(bpy)] (2) and [Cu(L¹)·(phen)]·(DMF) (3), where bpy = bipyridine and phen = phenanthroline. The paddle wheel arrangement in 1 is very similar to that in dimeric Cu(II) acetate; the symmetric arrangement in 1 rearranged in its corresponding monomeric species on reacting with phen and bpy. The symmetric bis-chelate ring in 1 and the desymmetrized monochelate ring in 2 and 3 are discussed following their crystal structures. The crystal structures for all the complexes and the electronic and fluorescence properties are discussed.

Keywords:

• Copper
• Carboxylate
• Paddle wheel
• Dimers
• Coordination
• Bis-chelate

Acknowledgments

The authors PS and PMS are grateful to Department of Science and Technology, New Delhi (India), for financial support vide Project Number SR/S1/IC-19/2005. The author SN is grateful to CSIR funding.