Coordination ability of amino acid hydrazide ligands and their influence on magnetic properties in copper(ii) coordination polymersElectronic supplementary information (ESI) available: 1H and 13C NMR and MS spectra of N,N′-di-l-leucine hydrazide and N,N′-di-l-phenylalanine hydrazide; synthetic procedure for L1 and L2 (Scheme S1); electronic spectra (Fig. S1); geometric parameters of the metal coordination spheres, stacking interactions and hydrogen bonding in 1 and 2 (Tables S1-S4); representati

Newly synthesized amino acid hydrazide ligands ( L1 = N , N ′-di- l -leucine hydrazide; L2 = N , N ′-di- l -phenylalanine hydrazide) have shown excellent reactivity and stability, as well as extraordinary coordination ability. Reactions of L1 / L2 with copper( ii ) ions and 4,4′-bipyridine (4,4′-bpy) as a secondary spacer yielded new coordination polymers {Cu(L1) 0.5 (4,4′-bpy)(H 2 O)(NO 3 )} n ·1.5 n H 2 O ( 1 ) and {Cu 3 (L2) 2 (4,4′-bpy)(H 2 O) 2 } n (NO 3 ) 2 n ·3 n H 2 O ( 2 ). UV/vis spectroscopy together with structural analysis showed that the deprotonated ligands L1 2− / L2 2− with six available donor atoms per ligand have the ability for strong chelation to copper( ii ) ions, acting as bis-bidentate ( L1 2− ) and bridging bi + tridentate ( L2 2− ) ligands. Compound 1 contains copper( ii ) ions simultaneously bridged with short hydrazide bridges (4.725 Å) and long 4,4′-bpy spacers (11.144 Å) forming a two-dimensional coordination network. In compound 2 , a pair of L2 2− molecules bridges three copper( ii ) ions, which are further interconnected with 4,4′-bpy into an overall one-dimensional chain-like structure. Although bulkier, the phenylalanine ligand ( L2 ) was found to be more flexible compared to the leucine ligand ( L1 ), exhibiting additional intramolecular contact: cation-π interaction. In both compounds, the hydrazide (-N-N-) bridge mediates the antiferromagnetic interaction between copper( ii ) ions. Hydrogen bonds have a strong influence on the crystal packing and physical (magnetic) properties. The reported compounds are first examples of hydrazide-bridged metal centres featuring amino acid-based ligands. Copper( ii ) coordination polymers constructed from newly synthesized amino acid hydrazides and 4,4′-bipyridine exhibit antiferromagnetic ordering mediated through hydrazide bridges.