Synthesis, spectral and magnetical characterization of monomeric [Cu(2-NO 2bz) 2(3-pyme) 2(H 2O) 2] and polymeric [Cu{3,5-(NO 2) 2bz} 2(3-pyme) 2] n

• Published in: Inorganica Chimica Acta Vol. 359; no. 4; pp. 1275 - 1281
• Main Authors: Stachová, P., Korabik, M., Koman, M., Melník, M., Mrozinski, J., Glowiak, T., Mazúr, M., Valigura, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2006
• Subjects: Carboxylate complexes; Copper; Crystal structure; Magnetic properties; Pyridylmethanol; Spectral properties; Carboxylate complexes; Pyridylmethanol; Copper; Spectral properties; Crystal structure; Magnetic properties
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2005.10.040

Two copper(II) complexes [Cu(2-NO 2bz) 2(3-pyme) 2(H 2O) 2] ( 1) and/or [Cu{3,5-(NO 2) 2bz} 2(3-pyme) 2] ( 2) (3-pyme = 3-pyridylmethanol) were prepared and structurally characterized. Both complexes exhibit very similar π–π stacking of 3-pyridylmethanol and nitrobenzoato ligands, but the magnetic moment temperature dependence of both complexes is different. Very weak antiferromagnetic interactions transmitted probably through π–π stacking were evaluated for both complexes and for complex ( 1), results in a small decrease of magnetic moment below the 5 K temperature. Weak ferromagnetic interactions of magnetic centres within the chain structure of ( 2) are somewhat stronger than the mentioned antiferromagnetic contribution. Two new complexes of composition [Cu(2-NO 2bz) 2(3-pyme) 2(H 2O) 2] ( 1) and/or [Cu{3,5-(NO 2) 2bz} 2(3-pyme) 2] ( 2) (3-pyme = 3-pyridylmethanol, ronicol or 3-pyridylcarbinol, 2-NO 2bz = 2-nitrobenzoate and 3,5-(NO 2) 2bz = 3,5-dinitrobenzoate) have been prepared and studied by elemental analysis, electronic, infrared and EPR spectroscopy, magnetic susceptibility measurements and the structure of both complexes has been solved. Complex ( 1) shows an unusual molecular type of structure consisting of the [Cu(2-NO 2bz) 2(3-pyme) 2(H 2O) 2] molecules held together by hydrogen bonds and van der Waals interactions. Complex ( 2) exhibits a polymeric chain-like structure [Cu{3,5-(NO 2) 2bz} 2(3-pyme) 2] n with copper atoms doubly bridged by two 3-pyridylmethanol molecules and the polymeric molecules are held together by van der Waals interactions. Complex ( 1) exhibits a magnetic moment μ eff = 1.84 B.M. at 300 K that remains nearly constant within the temperature region (5–300 K). Further cooling results in lowering the magnetic moment to μ eff = 1.82 B.M. at 1.8 K. The magnetic susceptibility temperature dependence obeys Curie–Weiss law with Curie constant of 0.423 cm 3 K mol −1 and with Weiss constant of −0.06 K. The magnetic moment of ( 2) exhibits a small increase with a decrease in the temperature ( μ eff = 1.80 B.M. at 300 K and μ eff = 1.85 B.M. at 1.8 K) with Curie constant of 0.409 cm 3 K mol −1 and with Weiss constant of +1.1 K, which can indicate a very weak ferromagnetic interaction between the copper atoms within the chain. Applying the molecular field model resulted in obtaining zJ′ values −0.08 cm −1 for complex ( 1), and −0.07 cm −1 for complex ( 2), respectively, that could characterize intermolecular and interchain interactions transmitted through π–π stacking.