Molecular Complexes of Crown Ethers in Crystals and Solutions

A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed.     

Thermodynamics of Formation of Molecular Complexes of Metalloporphyrins with Pyridine in Organic Solvents at 298.15 K

Microcalorimetric titration was used to obtain a full set of thermodynamic characteristics of the axial coordination of pyridine by metal complexes of synthetic (ZnTPP, NiTPP, CuTPP, (Cl)FeTPP, (Ac)FeTPP, (Cl)MnTPP, (Ac)MnTPP) and biological (ZnHP, ZnDP, ZnMP, ZnPP) porphyrins in benzene and chloroform at 298.15 K. It was established that the involved character of the processes under study is determined both by the structure of the metalloporphyrins and by the specific features of the solvation interactions of metalloporphyrin and pyridine with solvent molecules.     

Thermodynamics of Formation of Molecular Synthetic Metalloporphyrin Complexes with Pyridine in Benzene and in Chloroform at 298.15 K

Microcalorimetric titration was used to determine the thermodynamic characteristics (K _c, H, and S) for the axial coordination of pyridine by the metal complexes of synthetic porphyrins (ZnTBP, ZnTPTBP, MgTPTBP, and CuTPTBP) in benzene and in chloroform at 298.15 K. The capability of the metalloporphyrins under study to coordinate pyridine in chloroform decreases as follows: ZnTPP > ZnTBP > ZnTPTBP > MgTPTBP > CuTPTBP. The complicated course of the studied processes was shown to be determined by the electronic structure of the central metal atom, the nature of the porphyrin macrocycle, and by the specific solvation interactions of metalloporphyrin and pyridine with the solvent molecules.     

Molecular Porphyrin and Metalloporphyrin Complexes

The formation of specific molecular complexes of synthetic and natural porphyrins and metalloporphyrins with molecular ligands of different nature is considered. Data on composition, energy and thermal stability of donor–acceptor and –-complexes of porphyrins and metalloporphyrins were obtained by thermogravimetric analysis of crystal solvates.