Copper(ii) complexes of 3- and 4-picolinehydroxamic acids: from mononuclear compounds to 1D- and 2D-coordination polymersElectronic supplementary information (ESI) available: Tables S1-S13: structural details for 1, 4a, 7-11. Fig. S1-S4: structures of 1, 7 and 8. Fig. S5-S10: magnetic data for 4a, 7-11. CCDC 962652-962658. See DOI: 10.1039/c3ce42343c

A series of copper( ii ) complexes with 3- and 4-picolinehydroxamic acids has been synthesized and characterized by a variety of spectroscopic methods, X-ray structure analysis and magnetic susceptibility measurements. The ligands show the tendency to form 1D- and 2D-polymeric structures with copper( ii ) ions due to the chelating-and-bridging binding mode involving the ( O , O ′)-hydroxamate chelate formation combined with N -coordination of the pyridine moiety. In some cases the ( O , μ 2 - O ′) chelating-and-bridging modes are realized, in which either amide or hydroxamic oxygen atoms play a μ 2 -bridging role. Molecular and crystal structures of two discrete complexes: mononuclear [Cu( 3-HPicHA ) 2 (ClO 4 ) 2 ] ( 1 ) and binuclear [{Cu( 4-HPicHA )( bpy )(ClO 4 )} 2 ](ClO 4 ) 2 ( 4a ), and five coordination polymers catena -[Cu( 3-PicHA )( phen )] n (ClO 4 ) n ( 7 ), catena -[Cu( 4-PicHA )( bpy )] n (OH) n ·3.25 n H 2 O ( 8 ), catena -[Cu( 4-PicHA )(DMSO) 2 ] 2 n (ClO 4 ) 2 n ( 9 ), [Cu( 3-PicHA )(DMSO)(ClO 4 )] nm · nm DMSO ( 10 ), and [{Cu( 4-PicHA )( phen )} 2 ] n (ClO 4 ) 2 n ( 11 ) were determined by single crystal X-ray analysis. In structures 1 and 4a the hydroxamate ligands exist in a zwitterionic form with the O-deprotonated hydroxamate groups and protonated pyridine rings. The following types of coordination polymers have been structurally characterized: (i) single-stranded zigzag-shaped 1D polymers ( 7 and 8 ); (ii) double-stranded 1D polymer comprising binuclear subunits formed on account of μ 2 ( O )-carbonyl oxygen bridging coordination to the axial position of the copper( ii ) ion ( 9 ); (iii) 2D netted coordination polymers of two different types comprising μ 2 ( O )-bridged binuclear subunits ( 10 and 11 ). Magnetic susceptibility measurements (2-300 K) of powdered samples revealed the presence of moderate antiferromagnetic interaction in the binuclear complex 4a (2 J = −7.164(6) cm −1 ), while the coordination polymers exhibit weak antiferromagnetic interaction with a cryomagnetic behaviour obeying the Curie-Weiss law. We report on a series of copper( ii ) complexes of 3- and 4-picolinehydroxamic acids. Starting from discrete mononuclear complexes, 1D- and 2D-polymeric structures were obtained with a chelating-and-bridging binding mode of ligands.