No abstract

, Pd (8a-j), and Pt (9a-j) dithiolenes belonging to the general class [M(R,R′timdt) 2 ] (R,R′timdt ) monoanion of di-substituted imidazolidine-2,4,5-trithione) have been synthesized by sulfuring the disubstituted imidazolidine-2-thione-4,5-diones (4) with Lawesson's reagent (5) in the presence of the appropriate metal either as powder or as chloride. The obtained compounds have been characterized by UV-vis-NIR, FT-IR, and FT-Raman spectroscopies, CP-MAS 13 C NMR, and cyclic voltammetry, while [Ni(Me,Pr i timdt) 2 ] (7c) was also characterized by X-ray diffraction on a single crystal. Isolation from the reaction mixtures of the complex trans-bis [O-ethyl(4-methoxyphenyl)phosphonodithioato]Ni(II) (10a) and of 4,5,6,7-tetrathiocino[1,2-b:3,4-b′]diimidazolyl-1,10-diphenyl-3,8-diethyl-2,9-dithione (6a) as byproducts supports a radical mechanism for the one-pot reaction leading to the title dithiolenes. All these complexes absorb in the NIR region in the range 991-1030 nm with extinction coefficients of rarely encountered magnitudes (up to 80000 M -1 cm -1 ). They are therefore ideal candidates for applications on Nd:YAG laser technology for which the excitation wavelength is 1064 nm. Hybrid-DFT calculations have been used to gain an insight on the properties of this class of dithiolenes compared with those of the simplest [M(S 2 C 2 H 2 ) 2 ] [M ) Ni (1); M ) Pd (2); M ) Pt (3)] and of the well-known [M(dmit) 2 ] [dmit ) C 3 S 5 2-, 1,3-dithiole-2-thione-4,5-dithiolate; M ) Ni (11); M ) Pd (12); M ) Pt (13)] dithiolenes.

The macrocycles L(1)-L(3) incorporating N(2)S(3)-, N(2)S(2)O-, and N(2)S(2)-donor sets, respectively, and containing the 1,10-phenanthroline unit interact in acetonitrile solution with heavy metal ions such as Pb(II), Cd(II), and Hg(II) to give 1:1 ML, 1:2 ML(2), and 2:1 M(2)L complex species, which specifically modulate the photochemical properties of the ligands. The stoichiometry of the complex species formed during spectrofluorometric titrations and their formation constants in MeCN at 25 degrees C were determined from fluorescence vs M(II)/L molar ratio data. The complexes [Pb(L(1))][ClO(4)](2).(1)/(2)H(2)O (1), [Pb(L(2))][ClO(4)](2).MeNO(2) (1a), [Pb(L(3))(2)][ClO(4)](2).2MeCN (1b), and [Cd(L(3))][NO(3)](2) (2b) were also characterized by X-ray diffraction studies. The conformation adopted by L(1)-L(3) in these species reveals the aliphatic portion of the rings folded over the plane containing the heteroaromatic moiety with the ligands trying to encapsulate the metal center within their cavity. In 1, 1a, and 2b the metal ion completes the coordination sphere by interacting with counteranion units and solvent molecules. On the contrary, the 1:2 complex 1b shows Pb(II) sandwiched between two symmetry-related molecules of L(3) reaching an overall [4N + 4S] eight-coordination.

Interaction of methimazole (MMI, 1-methyl-imidazole-2-thione) with I2 in solvents having different polarity gives two new stable compounds containing a dication disulfide and a monocation disulfide arranged in dimers, respectively. These two species could represent effective intermediates in the reaction of MMI with an active iodine species in the thyroid gland and therefore shed more light on the mechanism of action of MMI as an antithyroid drug.