Copper(II) Complexes of salen Analogues with Two Differently Substituted (Push−Pull) Salicylaldehyde Moieties. A Study on the Modulation of Electronic Asymmetry and Nonlinear Optical Properties

Abstract

This paper presents some copper(II) complexes of salen analogues in which the two salicylaldehyde moieties carry different (electron donor, D, and acceptor, A) substituents in position 5, producing a push-pull charge asymmetry. The X-ray structures of some compounds show the presence of pairs of stacked molecules with head-to-tail intermolecular associations. The geometries of all complexes have been optimized through density functional theory (DFT) studies, which have shown that a major influence on the coordination bond lengths is given by the presence of the electron acceptor NO2 group. Such an influence operates mainly on the Cu-phenolato bonds: elongation of the Cu-O distance of the 5-nitrosalicylaldehyde moiety, with a concomitant decrease of the other Cu-O distance; the Cu-N bonds are less affected. The D groups have only a minor influence. The nonlinear optical responses, microgBetavec, of some molecules have been determined by EFISH measurements, and the Beta-vec values have been obtained using the DFT-calculated microg values because solubility problems hampered the experimental measurements of microg of some derivatives; the former, however, have been found to be in agreement with the experimental values that could be obtained. Deconvolution of the absorption bands in the near-UV region has allowed recognition of the charge-transfer (CT) transition, assigned to a ligand-to-metal CT (LMCT) by time-dependent DFT computations; we have then used the solvatochromism of this transition to obtain Beta0 and BetaCT values using the two-state model. These values were compared with those obtained by computational studies, which have also allowed evaluation of the influence of the substituents on the directions of microg and Betatot.

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

“…In many cases the charge transfer properties of these compounds justify this interest. Especially with these nitrogen donor ligands have been shown to be effective catalysts for oxidation reactions [11][12][13][14][15][16][17][18][19] and for ringopening metathesis polymerization [20] and recent studies of arene ruthenium complexes have shown that they are found to inhibit cancer cell growth [21][22][23][24][25][26], as non-linear optical (NLO) materials [27,28]. For a majority of the complexes studied, the metal centers are linked by a bridging ligand and the nature of the bridge has a fundamental influence on the electronic interaction between the metals and therefore on the characteristics of the material.…”

Copper(II) Complexes of Tridentate Schiff Bases of 5‐Substituted Salicylaldehydes and Diamines – The Role of the Substituent and the Diamine in the Formation of Mono‐, Di‐ and Trinuclear Species – Crystal Structures and Magnetic Properties

“…[1,2] Attempts at preparing such complexes according to the general procedure shown in Scheme 2 were unsuccessful. The weak point of the outlined synthesis is that the required initial condensation of salicylaldehyde with only one amino group of the diamine, to form the so-called "half unit" liScheme 1.…”

“…Compounds X can then be synthesised by reaction of 1 with another salicylaldehyde (Scheme 1). [1] In the absence of an auxiliary ligand, the fourth coordination site of copper can be occupied by a bridging phenolato oxygen atom of another "CuL" moiety, giving rise to dinuclear species [Cu 2 L 2 ] 2+ (2) [14] (see Scheme 4). Trinuclear species [Cu 3 L 3 (µ 3 -OH)] 2+ have also been described.…”

A Modular Approach Towards Nonsymmetrical Bis(metallosalen) Building Blocks

“…[9] We recently communicated a versatile approach towards new di-and tetraimine ligands based on 3,3Ј-diaminobenzidine and commercially available salicylaldehydes (Scheme 1, cf. 1, 2).…”