Synthesis of a Novel Discrete Metallacycle Complex Self‐assembled into a 3D Hydrogen‐binding Supramolecular Structure

A novel discrete dinuclear metallacyclic copper(II) complex, [Cu 2 L 2 (H 2 O) 2 ]·3H 2 O ( 1 ) has been firstly prepared where L is derived from the 1:2 condensation of 2,2′‐bipyridyl‐3,3′‐diformylhydrazide and acetone during the formation of the complex. Single‐crystal X‐ray diffraction analysis determines that the complex consists of dinuclear metallacyclic units [Cu 2 L 2 (H 2 O) 2 ] where two metal centers are linked together through two bis(chelating) bridge ligands L to form a bizarre cavity with size 0.9417 nm×0.4999 nm×0.6930 nm. Interestingly, the metal coordination also creates hydrogen bond sites that further aggregate these metallacycles into a 3D supramolecular structure with 2D perpendicular hydrophilic tunnels in crystal.