Synthesis and characterization of homotrimetallic copper complexes derived from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone O.B. Chanu a , A. Kumar b , A. Lemtur a , R.A. Lal a,⇑ a Department of Chemistry, North-Eastern Hill University, Shillong – 793022, Meghalaya, India b Department of Chemistry, Faculty of Science and Agriculture, The University of West Indies, St. Augustine, Trinidad and Tobago highlights " Homotrimetallic copper complexes have been synthesized and characterized. " The complexes show metal-metal interaction. " The ligand is present in enol form in all of the complexes. " The complexes have either distorted octahedral as well as distorted square pyramidal stereochemistries. graphical abstract Reactions of Copper (II) chloride dihydrate with H 4 nph in (5:1) molar ratio in methanol medium under reflux yielded trinuclear copper complex [Cu 3 (nph)(l 2 -Cl) 2 (H 2 O) 6 ]2H 2 O and has been characterized by various mass, thermoanalytical data, and various spectroscopic studies. N O O O X X N O Cu Cu Cu OH 2 OH 2 OH 2 OH 2 OH 2 OH 2 X = Cl article info Article history: Received 10 May 2012 Received in revised form 17 July 2012 Accepted 26 July 2012 Available online 3 August 2012 Keywords: Homotrinuclear copper (II) complexes bis(2-Hydroxy-1- naphthaldehyde)oxaloyldihydrazone Molar conductance Magnetic moment Electron paramagnetic resonance abstract Copper (II) complexes [Cu 3 (nph)(l 2 -X) 2 (H 2 O) 6 ]2H 2 O [X = Cl (1), (ClO 4 ) (3)] and [Cu 3 (nph)(NO 3 ) 2 (H 2 O) 6 ] (2) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)oxaloyldihydrazone in methanol med- ium and characterized. The structures of the complexes have been discussed in the light of data obtained from analytical, thermoanalytical, mass spectral studies, molar conductance, magnetic moment, elec- tronic, EPR, IR, FT-IR spectroscopic studies. The molar conductance values for the complexes fall in the region 0.5–0.9 Sm 2 mol 1 in DMSO solution indicating that all of them are non-electrolyte. The magnetic moment values for the complexes suggest weak M-M interaction in the structural unit of the complexes. The dihydrazone ligand is present in enol form in all of the complexes. Copper centre has tetragonally distorted octahedral stereochemistry in chlorido and perchlorato complexes while in nitrato complex, copper has mixed square-pyramidal and distorted-octahedral stereochemistry. The EPR parameters of the complexes indicate that the copper centre has the doublet state as the ground state. Ó 2012 Published by Elsevier B.V. Introduction The importance of homobimetallic and polymetallic copper (II) complexes stems from the fact that copper is an essential bio-ele- ment responsible for numerous catalytic processes in living organ- isms where it is often present in di- or trinuclear assemblies [1–3]. Multicopper complexes are important for catalysis [4–7] as well as magnetic aspect [8], and novel functional materials showing molecular ferromagnetism [9]. Trimetallic copper (II) complexes also enjoy a clear fascination of the magnetochemists, as such com- plexes offer the opportunities to test magnetic exchange models on more complicated systems. The multidentate organic molecules containing several coordi- nating sites with o-hydroxy aromatic aldehydes, ketones, azome- thine and amide functions in their molecular skeleton form 1386-1425/$ - see front matter Ó 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.saa.2012.07.113 ⇑ Corresponding author. Tel.: +91 0364 2722616; fax: +91 9436311770. E-mail address: ralal@rediffmail.com (R.A. Lal). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 854–861 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa