Spectrochimica Acta Part A 79 (2011) 666–671 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa Syntheses, spectral, electrochemical and thermal studies of mononuclear manganese(III) complexes with ligands derived from 1,2-propanediamine and 2-hydroxy-3 or 5-methoxybenzaldehyde: Self-assembled monolayer formation on nanostructure zinc oxide thin film Mohammad Hossein Habibi a,∗ , Elham Askari a , Mehdi Amirnasr b , Ahmad Amiri b , Yuki Yamane c , Takayoshi Suzuki c a Department of Chemistry, University of Isfahan, Isfahan, 81746-73441 I.R. Iran b Department of Chemistry, Isfahan University of Technology, Isfahan, 84156-83111, Iran c Department of Chemistry, Faculty of Science, Okayama University, Tsushima-naka 3-1-1, Okayama 700-8530, Japan article info Article history: Received 1 February 2011 Received in revised form 1 March 2011 Accepted 27 March 2011 Keywords: Mononuclear complexes Manganese(III) UV–vis spectroscopy Thermal study Electrochemical study Crystal structure N2O2 donors abstract Mononuclear Mn(III) complexes have been prepared via the Mn(II) reaction of an equimolar of Schiff-bases derived from reaction of 2-hydroxy-3-methoxybenzaldehyde or 2-hydroxy-5- methoxybenzaldehyde with 1,2-diaminopropane. Axial ligands L include: pyridine (py) and H 2 O. The resulting complexes have been characterized by FT-IR and UV–vis spectroscopy. The crystal structures of the complexes were determined and indicate that in the solid state the complex adopts a slightly distorted octahedral environment of the imine N and hydroxo O with the two axial ligands. The electro- chemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Mn III –Mn II is electrochemically quasi-reversible. Thermal stability of these complexes was determined by TG and DTG. Layers of these complexes were formed on nanostructure zinc oxide thin film and a red shift was observed when zinc oxide thin film is modified by complex. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Metal-chelate complexes generally offer many attractive prop- erties, such as catalysis to development of electrochemical sensors, single-molecule magnets and displaying a double role of elec- tron transport and light emission [1–7]. Manganese complexes are attracting not only in the fields of bioinorganic chemistry but also for their ability to function as progenitors of novel mag- netic molecular materials [8,9]. These complexes are significant for their redox active role in some biochemical processes, and current interests in the chemistry of higher oxidation-state man- ganese compounds draw from their utility as models for the photosynthetic water oxidation centers [10,11]. The role played by manganese in a number of biological systems has driven by the research efforts of many scientists from a variety of fields [12–20]. Manganese(III) Schiff-base complexes also pro- vide a rich series of structural types that can be used as models for the magnetic and structural properties of mangano enzymes ∗ Corresponding author. Tel.: +98 311 7932707; fax: +98 311 6689732. E-mail addresses: habibi@chem.ui.ac.ir, habibi284@gmail.com (M.H. Habibi). [21–24]. Exchange between two or more paramagnetic centers is the crucial criteria in manifestation of molecular magnetism. Tetradentate salen type Schiff-base ligands occupy four equatorial coordination sites of the six-coordinate metal cation, leaving axial positions to be occupied by either terminal ligands or bridging lig- ands that can link adjacent paramagnetic metal centers to form dinuclear structures. Structures and magnetic properties of man- ganese(III) salen type Schiff-base complexes have been studied, but reports on Mn III (MeOsalpn) complexes (MeOsalpn = N,N ′ -bis(2- hydroxy-3-methoxybenzylidene)propane-1,2-diamine) or N,N ′ - bis(2-hydroxy-5-methoxybenzylidene)propane-1,2-diamine] are rare. Most reported Mn III complexes are mononuclear with various apical ligands [25–31]. There are only a limited number of dinuclear and 1D chain structures [32–34]. Differential thermal gravimetry (DTG) and thermogravimetry (TG) are useful to study the modes of thermal decompositions as well as the composition of some metal complexes of Schiff bases [35]. Several researches have pro- posed that the redox potential in Schiff-base complexes is directly related to chemical characteristics of the entire complex. Thus, there has been a strong interest in determining thermodynamically meaningful redox potentials of manganese Schiff-base complexes and in understanding the relationship between these potentials 1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.saa.2011.03.055