Search

A series of new complexes of general formula [Au III (N^N)Br 2 ](PF 6 ) (N^N = 2,2'-bipyridine and 1,10-phenanthroline derivatives) were prepared and characterized by spectroscopic, electrochemical, and diffractometric techniques and tested against Gram-positive and Gram-negative bacterial strains ( Staphylococcus aureus , Streptococcus intermedius , Pseudomonas aeruginosa , and Escherichia coli ), showing promising antibacterial and antibiofilm properties.

The reactivity of 1,1'-bis(3-methyl-4-imidazolin-2-selone)methane ( L1 ) and 1,2-bis(3-methyl-4-imidazolin-2-selone)ethane ( L2 ) toward I 2 has been explored in MeCN under different experimental conditions and compared with that in CH 2 Cl 2 . The compounds [ L1' ](I) 2 ( I ), [ L1 I] n (I) n ( II ), [ L1 (μ-Se)](I) 2 ·1/2H 2 O ( III ), [ L1 I](I 3 )·2I 2 ( IV ), and [ L2 ](I) 2 ·MeCN ( V ) were obtained and characterized. X-ray diffraction analyses point out an ionic nature for these compounds, which is presumably favored by the polarity of the solvent used. In particular, [ L1 I] n (I) n ( II ) represents the first example of an iodonium complex of imidazoline-2-selone derivatives, while [ L1 (μ-Se)](I) 2 ·1/2H 2 O ( III ) represents a unique example of a dicationic [RSeSeSeR] triselane. Density functional theory calculations have allowed us to better understand the nature of the obtained compounds and to justify their formations in polarizing reaction conditions rather than in low polar solvents.

The reaction of the bis(1,2-dithiolene) complex [Pd(Me 2 timdt) 2 ] ( 1 ; Me 2 timdt •- = monoreduced 1,3-dimethyl-2,4,5-trithioxoimidazolidine) with Br 2 yielded the complex [Pd(Me 2 timdt)Br 2 ] ( 2 ), which was reacted with Na 2 mnt (mnt 2- = 1,2-dicyano-1,2-ethylenedithiolate) to give the neutral mixed-ligand complex [Pd(Me 2 timdt)(mnt)] ( 3 ). Complex 3 shows an intense solvatochromic near-infrared (NIR) absorption band falling between 955 nm in DMF and 1060 nm in CHCl 3 (ε = 10700 M -1 cm -1 in CHCl 3 ). DFT calculations were used to elucidate the electronic structure of complex 3 and to compare it with those of the corresponding homoleptic complexes 1 and [Pd(mnt) 2 ] ( 4 ). An in-depth comparison of calculated and experimental structural and vis-NIR spectroscopic properties, supported by IEF-PCM TD-DFT and NBO calculations, clearly points to a description of 3 as a dithione-dithiolato complex. For the first time, a broken-symmetry (BS) procedure for the evaluation of the singlet diradical character (DC) of heteroleptic bis(1,2-dithiolene) complexes has been developed and applied to complex 3 . The DC, predominant for 1 ( n D C = 55.4%), provides a remarkable contribution to the electronic structures of the ground states of both 3 and 4 , showing a diradicaloid nature ( n D C = 24.9% and 27.5%, respectively). The computational approach developed here clearly shows that a rational design of the DC of bis(1,2-ditiolene) metal complexes, and hence their linear and nonlinear optical properties, can be achieved by a proper choice of the 1,2-dithiolene ligands based on their electronic structure.

Metal bis(1,2-dithiolene) complexes belonging to the class [Ni(Ar-edt) 2 ] x - [Ar-edt 2- = arylethylene-1,2-dithiolate; Ar = phenyl, ( 1 x - ), 2-naphthyl ( 2 x - ); x = 0 and 1] were fully characterized by NMR, UV-visible-near-infrared (UV-vis-NIR), diffuse reflectance, and FT-IR spectroscopy, as well as cyclic voltammetry and single-crystal X-ray diffraction analysis. These complexes have emerged as new photoconducting materials that allowed for the development of a prototype of photodetectors with response in the vis-NIR region. The photodetecting devices showed in some cases quantum efficiencies orders of magnitude higher than those of previously reported 1,2-dithiolene systems.