Hydrogen Bonds of C=S, C=Se and C=Te with C-H in Small-Organic Molecule Compounds Derived from the Cambridge Structural Database (CSD)

Considerable interest in hydrogen bonding involving chalcogen has been growing since the IUPAC committee has redefined hydrogen bonding. Not only the focus is on unconventional acceptors, but also on donors not discussed before. It has been mentioned in previous studies that the proton of the H-C group could be involved in hydrogen bonding, but with conventional acceptors. In this study, we explored the ability of hydrogen bond formation of Se, S and Te acceptors with the H-C donor using Cambridge Structural Database in conjunction with Ab Initio calculations. In the CSD, there are respectively 256, 6249 and 11 R1,R2,-C=Se, R1,R2,-C=S and R1,R2,-C=Te structures that form hydrogen bonds, in which the N,N groups are majority. Except for C=S acceptor which can form a hydrogen bond with its C, C group, both C=Se and C=Te acceptors could form a hydrogen bond only with N,C and N,N groups. CSD analysis shows very similar d (norm) around -0.04 Å, while DFT-calculated interaction for N,C and N,N groups are also similar. Both interaction distances derived from CSD analysis and DFT-calculated interaction energies demonstrate that the acceptors form stable complexes with H-CF3. Besides hydrogen bonds, dispersion interactions are forces stabilizing the complexes since their contribution can reach 50%. Analysis of intra-molecular geometries and Ab Initio partial charges show that this bonding stems from resonance induced Cδ+=Xδ- dipoles. In many respects, both C=Se, C=S and C=Te are similar to C=S, with similar d (norm) and calculated interaction strengths.

Distortions and Deformations of Metaled Meso-Substituted and Unsubstituted Porphyrins and Derivatives in Crystal Structures

Experimental crystallographic structural parameters of a range of metaled meso-substituted and unsubstituted porphyrins were reviewed to show how far the meso-substitution by any functional group and the insertion of metal in the porphyrins core macrocycle may affect the geometry. The analysis of twists and angles has shown two kinds of distortions: external [T(Cβ-Cα-Cmeso-Xn) and T(Cβ-Cα-Cmeso-Cα)] and internal [T(Nm-Cα-Cmeso-Xn) and T(Nn-Cα-Cmeso-Cα)] with averages of [+6°and –6°] and [–5°and +5°], respectively. In the meso-substituted case, the external and internal twists Cβ-Cα-Cmeso-X and N-Cα-Cmeso-X, respectively are oppositely orientated. Similar effect is observed in meso-unsubstituted of Cβ-Cα- Cmeso-H and N-Cα-Cmeso-H. However, the external distortions are more significant than internal. Considering the same order, the limit of distortions is [97°and 132°(–48°)] for external and [91°(–89°) and 52°] for internal. In the two cases, the substituents have opposite directions of distortions. The meso-substituted porphyrins have a high limit of twisting than usubstituted one, depending of the weight of substituents. The average of the bond angular deformations is 168°, almost planar. However, the limit of angular deformation is 94°.

Chemical Fingerprint and Anti-Sickling Activity of Rosmarinic Acid and Methanolic Extracts from Three Species of Ocimum from DR Congo

The aim of this study was to characterize the polyphenolic composition by determination of chemical fingerprints of Methanolic extracts of Ocimum canum Sims, Ocimum basilicum L. and Ocimum gratissimum L. from Democratic Republic of Congo and to compare their antisickling activity of that of rosmarinic acid, the major compound to those of methanolic extracts. Phytochemical analysis performed by TLC and HPLC analysis, showed that rosmarinic acid is the most abundant phenolic acid in these Ocimum species according to the following order O. basilicum L., O. gratissimum L. and O. canum Sims. Methanolic extracts of these three species and pure rosmarinic acid showed significant antisickling activities with minimal concentration of normalization values of 0.18 ± 0.03, 0.23 ± 0.04, 0.26 ± 0.04 and 0.31 ± 0.05 mg/mL for rosmarinic acid, O. basilicum L., O. gratissimum L. and O. canum Sims methanolic extracts respectively. The antisickling activity order is the same as that of the rosmarinic acid content, indicating that this polyphenolic acid would be among the main active molecules in these extracts.

Chalcogen Bonds in Small-Organic Molecule Compounds Derived from the Cambridge Structural Database (CSD)

Growing interest in non-covalent interactions involving chalcogen atoms has been ascribed to their importance in crystal engineering, molecular recognition and macromolecular edifices. The present study is dealing with chalcogen bonds involving divalent Sulphur, Selenium and Tellurium atoms, acting as sigma-hole donors, in small-molecule compounds using the Cambridge Structural Database (CSD) in conjunction with ab initio calculations. Results derived from CSD surveys and computational study revealed that nucleophiles formed complexes with the chalcogen-bond donors R1-X-R2 (X = S, Se or Te). The main forces stabilizing the complexes were chalcogen bonds, enhanced by dispersion interactions. Complexation pattern and energetics show that nucleophile bonding at divalent S, Se and Te atoms is a relatively strong and directed interaction. The bond consists of a charge transfer from a nucleophile atom lone pair to an X-R1 or X-R2 antibonding orbital.

Interaction of Iron(III)-5,10,15,20-Tetrakis (4-Sulfonatophenyl) Porphyrin with Chloroquine, Quinine and Quinidine

Iron(III)-5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (FeTPPS) is used as non-physiological metalloporphyrin model for the natural iron (III)-protoporphyrin IX (FePPIX) resulting from hemoglobin degradation to investigate ligand binding reactions in aqueous solution. Studies were conducted on the interaction of FeTPPS with Chloroquine, Quinine, and Quinidine, which are historically the most common quinoline-based drugs used to treat malaria, an infectious disease afflicting several hundred millions every year worldwide, mainly in tropical regions. Using UV-Visible spectrophotometry, the binding reaction was studied at pH 7.40 in purely aqueous solution, and in aqueous solution containing NaNO3 at concentration of 0.1 M. Fitted titration curves obtained were in agreement with experimental data according to a formation scheme of 1:1 complex (1 FeTPPS μ-oxo-dimer: 1 Antimalarial). Values of apparent binding constant (K) obtained were between 4.3 × 103 M-1 to 7.59 × 104 M-1, demonstrating that FeTPPS and the antimalarials formed stable complexes. The stability of the complex decreased when NaNO3 was added to the solution. This ionic strength dependence was ascribed to electrostatic effects. Quinine and Chloroquine interacted with FeTPPS stronger than Quinidine did. Chloroquine showed the strongest affinity to FeTPPS. These findings revealed the influence of steric and stereochemical factors. Molecular electrostatic potentials (MEP) calculated with Hartree-Fock theory argue in favor of π-π and electrostatic interactions between reaction partners as driving forces for the complex formation. In the case of FeTPPS: Chloroquine interaction, it is suggested that an intramolecular hydrogen bond is formed between phenyl??and quinuclidine N-H+ as additional force stabilizing the complex. Analysis of crystallographic data using the Cambridge Structural Database (CSD) gave evidence of the hydrogen bond formation between phenyl??and N-H+ groups in 370 structures.