Girolamo Casella

DFT Calculation of 1J(119Sn,13C) and 2J(119Sn,1H) Coupling Constants in Di- and Trimethyltin(IV) Compounds

We have tested several computational protocols, at the nonrelativistic DFT level of theory, for the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) spin-spin coupling constants in di- and trimethyltin(IV) derivatives with various ligands. Quite a good agreement with experimental data has been found with several hybrid functionals and a double-zeta basis set for a set of molecules comprising tetra-, penta-, and hexa-coordinated tin(IV). Then, some of the protocols have been applied to the calculation of the 2J(119Sn, 1H) of the aquodimethyltin(IV) ion and dimethyltin(IV) complex with D-ribonic acid and to the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) of the dimethyltin(IV)-glycylglycine and glycylhistidine complexes in water solutions. Solvent effects have been considered in these cases by including explicit water molecules and/or the solvent reaction field, resulting in a good agreement with experimental data. The proposed protocols constitute a helpful tool for the structural determination of di- and triorganotin(IV) derivatives.

Ionic liquid crystals based on viologen dimers: tuning the mesomorphism by varying the conformational freedom of the ionic layer

ABSTRACT We investigated the liquid crystal behaviour of newly synthesised bistriflimide salts of symmetric viologen dimers. A smectic A phase was observed for intermediate spacer lengths and for relatively long lateral alkyl chains. The systems were characterised by thermal analysis, polarised optical microscopy, X-ray scattering and solid-state NMR. An intermediate ordered smectic phase was also exhibited by the compounds (except for systems with very short lateral chains) consisting of molten layers of alkyl chains and partially ordered ionic layers. These results, relating to the mesomorphic behaviour of viologen salts, are qualitatively compared to those of the more common imidazolium salts, highlighting the importance of the conformational degrees of freedom of the anions and of the cationic core. It appears that fine tuning of the conformational degrees of freedom of the ionic layer is an important component of mesophase stabilisation. Graphical Abstract

Diorganotin(IV) N-acetyl-L-cysteinate complexes: Synthesis, solid state, solution phase, DFT and biological investigations

Diorganotin(IV) complexes of N-acetyl-L-cysteine (H(2)NAC; (R)-2-acetamido-3-sulfanylpropanoic acid) have been synthesized and their solid and solution-phase structural configurations investigated by FTIR, Mössbauer, (1)H, (13)C and (119)Sn NMR spectroscopy. FTIR results suggested that in R(2)Sn(IV)NAC (R = Me, Bu, Ph) complexes NAC(2-) behaves as dianionic tridentate ligand coordinating the tin(IV) atom, through ester-type carboxylate, acetate carbonyl oxygen atom and the deprotonated thiolate group. From (119)Sn Mössbauer spectroscopy it could be inferred that the tin atom is pentacoordinated, with equatorial R(2)Sn(IV) trigonal bipyramidal configuration. In DMSO-d(6) solution, NMR spectroscopic data showed the coordination of one solvent molecule to tin atom, while the coordination mode of the ligand through the ester-type carboxylate and the deprotonated thiolate group was retained in solution. DFT (Density Functional Theory) study confirmed the proposed structures in solution phase as well as the determination of the most probable stable ring conformation. Biological investigations showed that Bu(2)SnCl(2) and NAC2 induce loss of viability in HCC cells and only moderate effects in non-tumor Chang liver cells. NAC2 showed lower cytotoxic activity than Bu(2)SnCl(2), suggesting that the binding with NAC(2-) modulates the marked cytotoxic activity exerted by Bu(2)SnCl(2). Therefore, these novel butyl derivatives could represent a new class of anticancer drugs.

Four-Component Relativistic DFT Calculations of (13)C Chemical Shifts of Halogenated Natural Substances.

We have calculated the (13)C NMR chemical shifts of a large ensemble of halogenated organic molecules (81 molecules for a total of 250 experimental (13)C NMR data at four different levels of theory), ranging from small rigid organic compounds, used to benchmark the performance of various levels of theory, to natural substances of marine origin with conformational degrees of freedom. Carbon atoms bonded to heavy halogen atoms, particularly bromine and iodine, are known to be rather challenging when it comes to the prediction of their chemical shifts by quantum methods, due to relativistic effects. In this paper, we have applied the state-of-the-art four-component relativistic density functional theory for the prediction of such NMR properties and compared the performance with two-component and nonrelativistic methods. Our results highlight the necessity to include relativistic corrections within a four-component description for the most accurate prediction of the NMR properties of halogenated organic substances.

Synthesis and crystal structure of [(PhenH)(PhenH2)][BiCl6]·2H2O with different o-phenanthroline protonations

AbstractThe reaction between bismuthate oxide and phen (1,10-phenanthroline) in acid medium led to the isolation of the unusual [(PhenH)(PhenH2)][BiCl6]·2H2O derivative, which has been characterized by X-ray analysis and IR spectroscopy. The compound crystallizes in the triclinic space group

Solution structure of R2Sn(IV)-β-N-acetyl-neuraminate (R = Me, Bu) complexes in D2O and DMSO-d6: Experimental NMR and DFT computational study

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Anti-cancer activity of di- and tri-organotin(IV) compounds with D-(+)-Galacturonic acid on human tumor cells

with a = 8.313(2), b = 9.349(2), c = 9.807(3) Å, α = 86.39(3), β = 110.27(3) and γ = 106.48(3)°. The crystal structure is made of [BiCl6]3− anions and [(PhenH)(PhenH2)]3+ cations. A network of hydrogen bond interactions involving the two clathrated water molecules, the phenanthroline moiety and the chlorines characterizes the entire structure.

Relativistic DFT Calculation of (119)Sn Chemical Shifts and Coupling Constants in Tin Compounds.

Three new triorganotin(IV) complexes of valproic acid (vp1, Me3Sn-valproate; vp2, Bu3Sn-valproate; vp3, Ph3Sn-valproate) have been synthesized and investigated by spectroscopic and biological methods. An anionic, monodentate valproate ligand was observed, ester-like coordinating the tin atom on a tetra-coordinated, monomeric environment. The structures, though, can distort towards a penta-coordination, as a consequence of a long range O···Sn interaction. Crystallographic and NMR findings confirm this situation both in solid state and solution. Biological finding evidenced a clear cytotoxic action of the complexes in hepatocellular carcinoma cell cultures: one of the complexes induced an 80% cell viability reduction after 24h treatment in HepG2 cells. This effect was accompanied by the appearance of biochemical signs of apoptosis. In Chang liver cells, the same compound induced only modest effects, suggesting a potential use as anti-cancer drug. Preliminary evaluations on hyperacetylation state of histone H3 in tributyltin-valproate treated HepG2 cells showed an increase in Ac-H3 (histone H3 acetylated at lys-9 and lys-14), suggesting that the compound maintains the deacetylation inhibition activity of its ligand valproate.