The antimony(III)-bridged heteropolyanion sandwich dimers [Sb(II3(A-α-XW9O34)2]11- (X = SiIV, GeIV and C-shaped double-sandwich [SbIII6O2(PW6O26)(A-α-PW9O34)2]15-.

Interaction of potassium antimony(iii) tartrate hydrate K(2)(SbC(4)H(2)O(6))(2)·3H(2)O with the trilacunary Keggin derivatives [A-α-XW(9)O(34)](10-) (X = Si(IV), Ge(IV)) and [A-α-PW(9)O(34)](9-) in aqueous acidic medium (pH 4.8) resulted in three novel polyanions, [Sb(3)(A-α-XW(9)O(34))(2)](11-) (X = Si(IV) (1), Ge(IV) (2)) and [Sb(6)O(2)(A-PW(6)O(26))(A-α-PW(9)O(34))(2)](15-) (3), which were isolated as the hydrated potassium salts K(11)[Sb(3)(A-α-XW(9)O(34))(2)]·31H(2)O (X = Si(IV) (K-1), Ge(IV) (K-2)) and the mixed potassium-sodium salt K(14)Na[Sb(6)O(2)(A-PW(6)O(26))(A-α-PW(9)O(34))(2)]·61H(2)O (KNa-3) salts, respectively, and characterized by single-crystal X-ray diffraction, IR spectroscopy, as well as elemental and thermogravimetric analyses. The Sb(III)-containing polyanions 1-3 possess unique structural features, as they represent the first examples of sandwich-type POMs with trigonal-pyramidal Sb(III)O(3) linkers. The stability of 1-3 in aqueous media was investigated by multinuclear ((183)W, (31)P) NMR and UV-Vis spectroscopy.

Interaction of thiazolidine-2-thione with 2,3,5,6-tetrabromo-1,4-benzoquinone: a set of sequential interactions involving redox and substitution reactions after an initial charge transfer complexation.

Interaction between thiazolidine-2-thione (T2T) as an electron donor and 2,3,5,6-tetrabromo-1,4-benzoquinone (p-bromanil, BRL) as a π-electron acceptor has been studied by using several spectral techniques, viz. UV/visible, IR, (1)H NMR and Mass spectra. A substitution reaction has been occurred after an initial formation of a CT complex, meanwhile a redox reaction has been occurred, in situ, too in which the interacting donor (T2T) has been oxidized to the corresponding thiazole. Thus, the stoichiometric ratio of this interaction has been found to be 2:1, T2T:BRL. However, the most interesting finding is that unexpectedly neither the SH group of the thiol form nor the NH group of the thione form of the T2T has shared in the substitution reaction with BRL. This finding has been confirmed by the different applied spectral tools, whereas a plausible reaction pathway has been illustrated and discussed.

Multiple and sequential charge transfer interactions occurring in situ: A redox reaction of thiazolidine-2-thione with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

Interaction of thiazolidine-2-thione (T2T) as an electron donor with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron π-acceptor has been studied. Electronic absorption spectra of the system T2T-DDQ in several organic solvents of different polarities have been measured. A charge transfer (CT) complexation has occurred between T2T and DDQ. This CT interaction has led to a redox reaction in which T2T has been oxidized to the corresponding dehydrogenated T2T (T2T-2H), meanwhile DDQ has been fully reduced to the corresponding hydroquinone (DDQH2). However, the two new species, resulting in situ, have been interacted, whereas a CT complex having the formula (T2T-2H·DDQH2) has occurred. IR, 1H NMR and mass spectra were used for ascertaining the structural formula of the synthesized CT complex. Formation constants (KCT), molar absorption coefficients (ɛCT) and thermodynamic properties of this CT interaction in various organic solvents were determined and discussed. The obtained KCT and ɛCT values have indicated that T2T-2H is a weak CT donor, whereas the formed CT complex has a low stability and it is classified as a contact-type CT complex.

In vitro simulation of the chemical scenario of the action of an anti-thyroid drug: charge transfer interaction of thiazolidine-2-thione with iodine.

Thiazolidine-2-thione (T2T) has been studied spectrophotometrically by UV-visible and IR spectra. The spectral studies have indicated that T2T has two tautomeric forms, namely thione and thiole forms, in addition to the dimeric thioamide complex existing as a hydrogen-bonded dimer of two thione forms. Interaction of the T2T as an electron donor with iodine as a typical σ-type acceptor has been studied spectrophotometrically. Electronic absorption spectra of the system T2T-I2 in several organic solvents of different polarities have performed a clear charge transfer (CT) band in each spectrum. Formation constants (KCT) and molar absorption coefficients (ɛCT) and thermodynamic properties, ΔH, ΔS, and ΔG, of this system in various organic solvents were determined and discussed. The stoichiometric ratio of the T2T-I2 system in solutions was found to be 1:1 T2T:I2, whereas the elemental analysis of the prepared solid CT complex has illustrated the same stoichiometry. The obtained KCT and ɛCT values have indicated that T2T is a donor of moderately strength capable of interacting with the iodine just to form the corresponding CT complex with an iodine molecule without further reducing of the iodine to either of the corresponding poly-iodide ions viz. I3-, I5-, etc. This action of spongy trapping of iodine simulates in vitro the chemical scenario of the anti-thyroid action of this compound.

Intra- and intermolecular charge transfer: twin themes and simultaneous competing transitions involving ferrocenes.

Electronic absorption spectra of ferrocene, ferrocenecarboxylaldehyde, butylferrocene, and 1,1'-diacetylferrocene in pure organic polar and non-polar solvents, pure halocarbon solvents and in several hexane-halocarbon solvent mixtures have been recorded. The investigated ferrocenes have shown several intra-molecular electronic transitions of the types pi-pi*, n-pi*, and d-d*. On using protonic solvents (HA) each of the ferocenes (Fc) acquires a proton exported from the solvent to form a complex with the formula [FcH](+)[A](-). However, on using halocarbon solvents each of the ferrocenes has shown an intermolecular charge-transfer-to-solvent (CTTS) which is characterized by the appearance of new absorption spectral band(s) for each ferrocene-halocarbon solvent interaction. Formation constants (K(CT)) and molar absorption coefficients (epsilon(CT)) of these interactions have been determined and discussed. The study has indicated that the observed different transitions are dependent upon the number and nature of the substituents involved in the ferrocenes.

Stepwise charge transfer complexation of some pyrimidines with sigma-acceptor iodine involving a new unconventional acceptor.

Interactions of some pyrimidine derivatives, 4-amino-2,6-dimethylpyrimidine, kyanmethin, (4AP), 2-amino-4,6-dimethylpyrimidine (2AP), 2-aminopyrimidine (AP), 2-amino-4-methylpyrimidine (AMP), 2-amino-4-methoxy-6-methylpyrimidine (AMMP), and 4-amino-5-chloro-2,6-dimethylpyrimidine (ACDP) as electron donors, with iodine (I(2)), as a typical sigma-electron acceptor, have been studied. Electronic absorption spectra of these interactions in several organic solvents of different polarities have performed instant appearance of clear charge transfer (CT) bands. Formation constants (KCT), molar absorption coefficients (epsilonCT) and thermodynamic properties, DeltaH, DeltaS, and DeltaG, of these interactions have been determined and discussed. Electronic absorption spectra of the solutions of the synthesized pyrimidines-iodine, P-I2, CT complexes have shown the characteristic bands of the triiodide ion, I3*. UV/vis spectral tracking of these interactions have shown that by lapse of time the first formed CT complex, P-I2, is transformed to the corresponding triiodide complex, P(+)I.I3*, then, the later interacts as a new unconventional acceptor and it forms a CT complex of the form (P).(P+I.I3*). Elemental analyses of these solid complexes have indicated the stoichiometric ratio 2:2, or formally 1:1, P:I2.