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A family of molecular heptacadmium carboxylate clusters templated inside [3+3] Schiff base macrocycles is isolated and analyzed by variable temperature solution and solid-state NMR spectroscopy, single-crystal X-ray diffraction (SCXRD), and density functional theory (DFT) calculations. The studies have helped in understanding the host-guest and dynamics properties of a new family of metallocavitands and have helped in designing new supramolecular catalysts and materials.

The form of 8-hydroxyquinoline in different solvents is examined by using spectroscopic and computational methods. The results have shown that 8-hydroxyquinoline has displayed a clear preference for the cis conformation, but a small fraction of the trans conformation is present in water solutions.

The synthesis, characterization and photoreactivity of a series of new heteroaryl imines form the coupling between 2-benzothienyldiphenylmethyliminophosphorane and heterocyclic aldehydes are described. The reaction at 60 degree Celsius gave the formation of only the trans isomer while at high temperature cis isomer was obtained and only the cis isomers showed a photochemical reactivity to give corresponding condensed pyridine derivative.

Nonrelativistic and relativistic time-dependent density functional calculations are performed on the excited states of the [M(H2timdt)(sub 2)] (M = Ni, Pd, Pt) compounds. In all members of the series, the excited state at the lowest energy corresponds to a HOMO -> LUMO excitation and indicates that a large number of the transitions have an intraligand character.

Research has been conducted on 2,3-epoxy alcohols. The authors describe their study of the role of metal ions in regioselective opening of these alcohols carried out via hybrid density functional theory method.

Density functional theory and time-dependent density functional theory were applied to describe the ground and excited states and the spectral characteristics of the meridianal and facial isomers of aluminum tris(quinolin-8-oclate) (Alq3). Experimental meridinal Alq3 absorption band locations were well reproduced by the computations, which allowed easy assignment of the absorption bands.

Density functional theory (DFT) calculations on the geometry and bonding energy of the X - - - I intermolecular interaction of CF3I and (CH3)(sub n)X and (CH3)(sub n)XO are reported. All the adducts with the oxides as donors show a weaker interaction with CF3I than the relative donor without oxygen except the CF3I - - - ON(CH3) adduct, which has a stronger interaction.

The Mn (OESPz) complex reacts with perfluorodecalin or 1,2-difluorobenzene affording the fluromanganese (III) (ethylsulfanyl) porphyrazinato complex and defluorinated organic products. The preliminary results of this investigation concern the use of Mn (OESPz) in the chemical and electrochemical reductive defluorination of perfluorodeclain.

New (M(R,R'timdt)2) metal-dithiolenes and related compounds, where M = Ni, Pd and Pt and R,R'timdt = monoanion of disubstituted imidazolidine-2,4,5-trithiones, have been synthesized. The characteristics of these compounds are revealed via UV-vis-NIR, FTIR and FT-Raman spectroscopies, CP-MAS 13C NMR and cyclic voltammetry. The physical and chemical properties of the compounds were examined using Hybrid-DFT calculations.

Dinitrodialkoxybenzene derivatives are important precursors for Schiff base macrocycles and a variety of other molecules. During our investigations, we have found that the dinitration reaction of 1,2-dialkoxybenzenes proceeds with unusual regioselectivity, giving exclusively the desired 1,2-dialkoxy-4,5-dinitrobenzene product, but we have been unable to find a good explanation for this result. The dinitration of 1,4-dialkoxybenzene derivatives also exhibits surprising regioselectivity that has hitherto been left unexplained. Herein, we report a detailed DFT analysis of the regioselective dinitration of both 1,2- and 1,4-dimethoxybenzene. These results show that the reaction mechanism likely involves a single electron transfer (SET) process. In the case of the former isomer, the regioselectivity is mainly determined by the symmetry of the HOMO of the aromatic moiety that defines the structure of the SHOMO of the aromatic radical cation formed by the SET process. In the case of the latter isomer, the selectivity is due mainly to solvation effects and may thus be altered depending on the solvent environment. Synthetic studies of the nitration of 1,4-dialkoxybenzene derivatives using different solvent conditions support this conclusion and provide practical information for tuning the regioselectivity of the reaction. [ABSTRACT FROM AUTHOR]

A new hexadentate, tripodal 8-hydroxyquinoline based ligand (QH) and its gadolinium(III) tris-chelated (GdQ) complex with hemicage structure was investigated by using high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS). The protonated adduct of the free ligand and its hemicage tripodal Gd(III) complex, [GdQ + H], were first observed in experiments of electrospray ionization (ESI) with a linear ion trap (LTQ) mass spectrometer and further investigated by using high resolution FTICRMS. Gas-phase dissociation of the protonated Gd(III) complex, by infrared multiphoton dissociation (IRMPD) FTICR MS, demonstrated a fragmentation pattern with six main product cluster ions labeled as [F] ( n = 1 up to 6). These product ions suggest the elimination of 7-amino-alkyl or 7-alkyl chains of the hemicage moiety. High resolution MS conditions allowed the elucidation of the fragmentation pattern and product ion structures along with the determination, among the isotopic pattern of Gd, of the chemical compositions of closely related species, which differ in terms of hydrogen content. Among the Gd six naturally stable isotopes, Gd is the most abundant, and its peak within each cluster was used as a reference for distinguishing each product ions. Computational DFT investigations were applied to give support to some hypothesis of fragmentation pathways, which could not have been easily justified on the basis of the experimental work. Furthermore, computational studies suggested the coordination geometry of the protonated parent complex and the five- and four-coordinated complexes, which derive from its fragmentation. Furthermore, experimental and computational evidences were collected about the octet spin state of the parent compound. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The synthesis and the electrochemical, photophysical, structural, and photoconductive properties of three new heteroleptic Pd(II) complexes with various 3',5'- disubstituted-2-(2'-pyridil) pyrroles H(N^N) as coordinated ligands are reported. The coordination of the metal center was completed by a functionalized Schiff base H(O^N) used as an ancillary ligand. The [(N^N)Pd(O^N)] complexes showed highly interesting photoconductive properties which have been correlated to their electronic and molecular structures. Theoretical density functional theory (DFT) and time-dependent DFT calculations were performed, and the results were confronted with the organization in crystalline phase, allowing to point out that the photoconductive properties are mainly a consequence of an efficient intramolecular ligand-to-metal charge transfer, combined to the proximity between the central metal and the donor moieties in the solid-state molecular stacks. The reported results confirm that these new Pd(II) complexes form a novel class of organometallic photoconductors with intrinsic characteristics suitable for molecular semiconductors applications.

Novel silver(I) acylpyrazolonato coordination polymers of formula [Ag(Q(R))]n (1-3) have been synthesized by interaction of silver nitrate with HQ(R) in methanol in the presence of an equivalent quantity of KOH (in general HQ(R) = 1-phenyl-3-methyl-4-RC(═O)-5-pyrazolone, in detail HQ(fb), R = -CF2CF2CF3; HQ(cy), R = -cyclo-C6H11; HQ(be), R = -C(H)═C(CH3)2). [Ag(Q(R))]n react with 2-ethylimidazole (2EtimH), 1-methylimidazole (Meim), and triphenylphosphine (PPh3), affording the mononuclear Ag(Q(fb))(EtimH) (4), Ag(Q(cy))(Meim)2 (5), Ag(Q(be))(Meim) (6), and Ag(Q(R))(PPh3)2 (7-9). All complexes have been analytically and spectroscopically characterized, and for some of them the X-ray crystal structure has been resolved. In particular, the single crystal molecular structure determination of Ag(Q(fb))(EtimH) and Ag(Q(be))(PPh3)2 has confirmed the different coordination modes of the HQ(fb) and HQ(be) acylpyrazolone ligands, the former being bound to the silver(I) ion in a monodentate fashion while the latter in the O2-chelating mode. Density functional theory computations suggest new insights about metal-ligand interactions and the observed linkage isomerism. While phosphine-containing complexes Ag(Q(R))(PPh3)2 (7-9) seem not to be able to efficiently inhibit the growth of Escherichia coli and Staphylococcus aureus, the polynuclear complexes [Ag(Q(R))]n (1-3) and the mononuclear Ag(Q(fb))(EtimH) (4), Ag(Q(cy))(Meim)2 (5), and Ag(Q(be))(Meim) (6) show a high and almost steady in time antibacterial activity, comparable to that of AgNO3. This activity is likely related to the degree of saturation of the silver center and to the presence of different ancillary ligands in the diverse typologies of complexes.

The supramolecular chemistry of bowl-shaped heptazinc metallocavitands templated by Schiff base macrocycles has been investigated. Dimerization thermodynamics were probed by (1)H NMR spectroscopy in benzene-d(6), toluene-d(8), and p-xylene-d(10) and revealed the process to be entropy-driven and enthalpy-opposed in each solvent. Trends in the experimentally determined enthalpy and entropy values are related to the thermodynamics of solvent autosolvation, solvent molecules being released from the monomeric metallocavitand cavity into the bulk solvent upon dimerization. The relationship established between experimentally measured dimerization thermodynamics and autosolvation data successfully predicts the absence of dimerization in CH(2)Cl(2) and CHCl(3) and was used to estimate the number of solvent molecules interacting with the monomeric metallocavitand in solution. Host-guest interactions between heptazinc metallocavitands and fullerene C(60) have also been investigated. Interestingly, metallocavitand-C(60) interactions are only observed in solvents that facilitate entropy-driven dimerization suggesting entropy and solvent autosolvation may be important in explaining concave-convex interactions., (© 2012 American Chemical Society)

A systematic study of a class of divalent transition-metal texaphyrin complexes (M-Tex(+), M = Mn, Fe, Co, Ni, Cu, Zn), recently proposed as active photosensitizers in photodynamic therapy (PDT), was undertaken for the ground and excited electronic states. Geometry optimizations were performed by using the PBE0 exchange-correlation functional coupled with the 6-31G(d) basis set, while electronic excitations energies were evaluated by means of time-dependent density functional response theory (TD-DFT) at the PBE0/6-31+G(d) // PBE0/6-31G(d) level of theory. Solvent effects on excitation energies were taken into account in two ways:  by considering solvent molecules explicitly coordinated to the metal center and as bulk effects, within the conductor-like polarizable continuum model (C-PCM). The influence of the metal cation on the so-called Q-band, localized in the near-red visible region of the spectrum, was carefully examined since it plays a basic role in the drug design of new photodynamic therapy photosensitizers. The differences between experimental and computed excitation energies were found to be within 0.3 eV.

The electronic structure of five complexes [M(oXHpz)] [M = Ni(2+); oXHpz(2)(-) = 2,3,7,8,12,13,17,18-octakis-substituted (X = CH2, NH, O, S, Se)-5,10,15,20-tetraazaporphyrinate dianion] has been investigated using a density functional approach. All the geometries have been obtained minimizing the total intramolecular energy using a nonlocal hybrid functional (B3LYP) at the 6-31g* level. The electronic configuration of Ni(2+) is (dx(2)-y(2))(0)(dxy)(2)(dxz,dyz)(4)(dz(2))(2). Optimized geometries exhibit a planar conformation and are all above the threshold for ruffling, which is described by a Ni-Np bond distance of 1.85-1.87 Å for sterically unhindered porphyrazines. Indeed, the smallest bond distance is 1.880 Å for Ni(oOHpz). Peripheral substituents yield modifications to the "core" of the macrocycle and to the energy levels, changing σ and π interactions. Furthermore, within a time-dependent density functional theory approach, excited states of Ni(oXHpz) [X = CH2, NH, O, S, Se,] complexes have been studied and compared with available experimental UV-vis spectra.