Structural Changes in CuII Complexes of Potential Octadentate Ligands by Coordination with Carboxylate/Carboxylic Acid: DFT, TD-DFT, and Experimental Studies

Enrique Montiel; Julian Cruz; Narayanan Jayanthi; Sylvain Bernés; Thangarasu Pandiyan

doi:10.1071/CH09555

RESEARCH ARTICLE

Previous Contents Vol 63(6)

Structural Changes in Cu^II Complexes of Potential Octadentate Ligands by Coordination with Carboxylate/Carboxylic Acid: DFT, TD-DFT, and Experimental Studies

Enrique Montiel ^A , Julian Cruz ^A , Narayanan Jayanthi ^B , Sylvain Bernés ^C and Thangarasu Pandiyan ^D ^E

+ Author Affiliations

- Author Affiliations

^A Área académica de Químicas, Universidad Autónoma del Estado de Hidalgo, Unidad Universitaria, Km 4.5 Carretera Pachuca-Tulancingo, CP. 42184 Pachuca-Hidalgo, México.

^B División de Ingeniería en Informática, Universidad Politécnica del Valle de México, Av. Mexiquense, Tultitlan, Estado de México, CP. 54910, México.

^C DEP, Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, Guerrero y Progreso S/N, Col. Treviño, 64570 Monterrey N.L., Mexico.

^D Facultad de Química, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, Coyoacán, 04510. México D.F., México.

^E Corresponding author. Email: pandiyan@servidor.unam.mx

Australian Journal of Chemistry 63(6) 965-977 https://doi.org/10.1071/CH09555
Submitted: 16 October 2009 Accepted: 3 March 2010 Published: 11 June 2010

Abstract

The structural and spectroscopic studies of N,N,N′,N′,N′-pentakis-(benzimidazol-2-yl-methyl)diethylenetriamine (L¹) and N,N,N′,N′-tetrakis-(benzimidazol-2-yl-methyl)-N′-(carboxylmethyl)diethylenetriamine (L²H) and [CuL¹]²⁺, [CuL²H]²⁺, and [CuL²]⁺ were carried out by density functional theory (DFT) and time-dependant (TD)-DFT techniques. The results show that a geometrical change occurs when carboxylate/carboxylic acid coordinates with the metal ion. For example, the ligand L²H forms an octahedral geometry with Cu^II and in the structure, four nitrogens (N3, N13, N44, N47) are equatorially coordinated with the metal ion, and atoms O50 (–COOH) and N41, which are weakly bonded at the axial positions, are in competition in the formation of an axial bond with Cu^II; however, for the ligand L², only a square pyramidal (SP) geometry results with Cu^II because of the formation of a strong axial bond by O50 (–COO^–) with Cu^II, which dictates non-bonding at its trans position. Molecular orbital analysis proves that both HOMO and HOMO – 1 are localized over the carboxylate ion that favours a strong axial bond with the metal ion; thus, the SP geometry results in the X-ray structure of [CuL²]ClO₄. Furthermore, for the complexes, since the electronic spectroscopic bands were unseparated in the spectra, the TD-DFT was used to identify the bands.

Acknowledgements

The authors acknowledge the Direccíon General de Asuntos del Personal Académico (Project PAPIIT No. IN226310) for the support. They also thank DGSCA-UNAM for the computation facilities.

References

Structural Changes in CuII Complexes of Potential Octadentate Ligands by Coordination with Carboxylate/Carboxylic Acid: DFT, TD-DFT, and Experimental Studies

Abstract

Acknowledgements

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Structural Changes in Cu^II Complexes of Potential Octadentate Ligands by Coordination with Carboxylate/Carboxylic Acid: DFT, TD-DFT, and Experimental Studies