Peking Univ, Coll Chem & Mol Engn, State Key Lab Rare Earth Mat Chem & Applicat, Beijing 100871, Peoples R China
; Chinese Acad Sci, Inst High Energy Phys, Beijing Synchrotron Radiat Factory, Beijing 100039, Peoples R China
Novel tetranuclear copper complexes, Cu-4(OH)(2)(ClO4)(3) (HA). H2O (1) and Cu-4(ClO4)(5)(H3B). 3H(2)O (2), were synthesized by reacting 1,5-bis(1'-phenyl-3'-methyl-5'-pyrazolone-4')-1 ,5-pentanedione with 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine in the presence of a template reagent copper ion. New [2+2] type open cyclic multidentate ligands are also obtained from the reaction (H4A and H6B stand for new compounds from 1,3-propanediamine and 2-hydroxyl-1,3-propanediamine, respectively). They each contain five C = O, three C = N and one NH2 groups. The complexes were characterized by elemental analyses, conductivity, FT-i.r. (micro-i.r., deconvolution technique), FAB-MS, e.s.r., electronic spectra and extended X-ray absorption fine structure (EXAFS). Copper ions in (1) are basically four coordinate with tetragonal geometry. The average coordination bond distances of Cu-N and Cu-O are 1.91 Angstrom and 2.05 Angstrom. In (2), copper ions are primarily five coordinate with square-based pyramidal geometry. The average coordination bond distances of Cu-N and Cu-O are 1.93 Angstrom and 2.08 Angstrom. Four copper atoms in molecules may be arranged tetragonally. Both the ligand field and the coordination bonds in complex (1) are stronger than those in (2). Investigations on variable temperature susceptibilities show that some antiferromagnetic exchange interaction exist in the complexes. The plots of chi(-1) versus T obey the Curie-Weiss law only at low temperature. Preliminary results of a bioassay indicate that the two complexes have some antitumour activity in vitro.