The Role of Hydrogen Bonds in Interactions between [PdCl4]2- Dianions in Crystal

[PdCl4]2- dianions are oriented within a crystal in such a way that a Cl of one unit approaches the Pd of another from directly above. Quantum calculations find this interaction to be highly repulsive with a large positive interaction energy. The placement of neutral ligands in their vicinity reduces the repulsion, but the interaction remains highly endothermic. When the ligands acquire a unit positive charge, the electrostatic component and the full interaction energy become quite negative, signalling an exothermic association. Raising the charge on these counterions to +2 has little further stabilizing effect, and in fact reduces the electrostatic attraction. The ability of the counterions to promote the interaction is attributed in part to the H-bonds which they form with both dianions, acting as a sort of glue.

Multicomponent Solids of DL-2-Hydroxy-2-phenylacetic Acid and Pyridinecarboxamides

We prepared cocrystals of DL-2-Hydroxy-2-phenylacetic acid (D, L-H2ma) with the pyridinecarboxamide isomers, picolinamide (pic) and isonicotinamide (inam). They were characterized by elemental analysis, single crystal and powder X-ray, IR spectroscopy and 1H and 13C NMR. The crystal and molecular structures of (pic)-(D-H2ma) (1), (nam)-(L-H2ma) (2) and (inam)-(L-H2ma) (3) were studied. The crystal packing is stabilized primarily by hydrogen bonding and in some cases through π-π stacking interactions. The analysis of crystal structures reveals the existence of the characteristic heterosynthons with the binding motif R22(8) (primary amide–carboxilic acid) between pyridinecarboxamide molecules and the acid. Other synthons involve hydrogen bonds such as O-H(carboxyl)···N(pyridine) and O-H(hydroxyl)···N(pyridine) depending on the isomer. The packing of 1 and 3 is formed by tetramers, for whose formation a crystallization mechanism based on two stages is proposed, involving an amide–acid (1) or amide–amide (3) molecular recognition in the first stage and the formation of others, and interdimeric hydrogen bonding interactions in the second. The thermal stability of the cocrystals was studied by differential scanning calorimetry and thermogravimetry. Further studies were conducted to evaluate other physicochemical properties of the cocrystals in comparison to the pure coformers. Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) were performed to further characterize and rationalize the noncovalent interactions.

Fumarato and Phthalato Bridged Dinuclear Metal-Organic Cu(II) and Mn(II) Compounds involving Infinite Fumarate-water Assemblies and Unusual Structure-guiding H-bonded Synthons: Antiproliferative Evaluation and Theoretical Studies

Two new dinuclear coordination compounds viz. [Cu2(µ-fum)(phen)2(H2O)6](fum)•6H2O (1) and [Mn2(µ-phth)2(phen)4]•2H2O (2) (phen = 1,10-phenanthroline, fum = fumarate and phth = phthalate) have been synthesized and characterized by elemental analysis, single...

Solvent-driven structural topologies in phenanthroline-based co-crystals of Zn(ii) involving fascinating infinite chair-like {[(bzH)4Cl2]2−}n assemblies and unconventional layered infinite {bz-H2O-Cl}n anion-water clusters: antiproliferative evaluation and theoretical studies

Anticancer activities considering cell cytotoxicity, apoptosis and molecular docking have been explored in Zn(ii) co-crystals of phenanthroline involving infinite chair-like assemblies and unconventional layered infinite anion-water clusters.

Triel bonds within anionanion complexes

The ability of two anions to interact with one another is tested in the context of pairs of TrX₄^- homodimers, where Tr represents any of the triel atoms B, Al, Ga, In, or Tl, and X refers to a halogen substituent F, Cl, or Br. None of these pairs engage in a stable complex in the gas phase, but the situation reverses in water where the two monomers are held together by Tr⋯X triel bonds, complemented by stabilizing interactions between X atoms. Some of these bonds are quite strong, notably those involving TrF₄^-, with interaction energies surpassing 30 kcal mol^-1. Others are very much weaker, with scarcely exothermic binding energies. The highly repulsive electrostatic interactions are counteracted by large polarization energies.

Anion-Anion Interactions in Aerogen-Bonded Complexes. Influence of Solvent Environment

Ab initio calculations are applied to the question as to whether a AeX₅^- anion (Ae = Kr, Xe) can engage in a stable complex with another anion: F^-, Cl^-, or CN^-. The latter approaches the central Ae atom from above the molecular plane, along its C₅ axis. While the electrostatic repulsion between the two anions prevents their association in the gas phase, immersion of the system in a polar medium allows dimerization to proceed. The aerogen bond is a weak one, with binding energies less than 2 kcal/mol, even in highly polar aqueous solvent. The complexes are metastable in the less polar solvents THF and DMF, with dissociation opposed by a small energy barrier.

Biologically relevant unusual cooperative assemblies and fascinating infinite crown-like supramolecular nitrate–water hosts involving guest complex cations in bipyridine and phenanthroline-based Cu(ii) coordination compounds: antiproliferative evaluation and theoretical studies

Cytotoxicity in cancer cells with structure activity relationship has been explored in Cu(ii) compounds involving biologically relevant cooperative assemblies and fascinating crown-like nitrate–water hosts with guest complex cations.

Supramolecular assemblies involving biologically relevant antiparallel π-stacking and unconventional solvent driven structural topology in maleato and fumarato bridged Zn(ii) coordination polymers: antiproliferative evaluation and theoretical studies

In vitro anticancer activities have been explored in solvent driven maleato and fumarato bridged Zn(ii) coordination polymers involving energetically significant antiparallel π-stacking and enclathrated guest MeOH/H₂O moieties.

Biologically relevant and energetically significant cooperative ternary (π–π)2/(π–π)1/(π–π)2 assemblies and fascinating discrete (H2O)21 clusters in isostructural 2,5-pyridine dicarboxylato Co(ii) and Zn(ii) phenanthroline compounds: antiproliferative evaluation and theoretical studies

Cytotoxicity in cancer cells with structure activity relationship has been explored in isostructural Co(ii) and Zn(ii) compounds involving energetically significant cooperative (π–π)₂/(π–π)₁/(π–π)₂ assemblies and fascinating (H₂O)₂₁ clusters.

Oxalato bridged coordination polymer of manganese(iii) involving unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts: antiproliferative evaluation and theoretical studies

Unconventional O⋯π-hole(nitrile) and antiparallel nitrile⋯nitrile contacts have been theoretically investigated for a Mn(iii) coordination polymer considering cytotoxicity, apoptosis, ROS generation, molecular docking and pharmacophore features.

Adipato bridged novel hexanuclear Cu(ii) and polymeric Co(ii) coordination compounds involving cooperative supramolecular assemblies and encapsulated guest water clusters in a square grid host: antiproliferative evaluation and theoretical studies

Novel adipato bridged Cu(ii) and Co(ii) complexes synthesized by considering cytotoxicity, apoptosis, ROS generation, molecular docking and pharmacophore features.