Studies On Non-covalent Interactions In Metal Complexes With Aromatic Ligands

Supramolecular chemistry is a new field of chemistry in the past decades. Individual molecules can spontaneously form the ordered supramolecular structure via supramolecular interactions. The ordered supramolecular structure usually assumes special properties and functions that a single molecule does not have. Supramolecular interaction mainly includes hydrogen bonding, cation-πinteraction,π-πstacking and CH...πinteraction. These weak interactions may effectively stabilize the supramolecular structure.This dissertation mainly discusses the supramolecular interaction in metal complexes with aromatic ligand(s). Three important factors (metal coordination, substituents and hetero-atoms in an aromatic ring) are considered in the experimental design and theoretical calculations.18 new compounds, (Ⅰ)-(XⅩⅧ), were synthesized in this work by hydrothermal, reflux and solution mixing methods, respectively, in with CuⅡ,ZnⅡ,CoⅡ,NiⅡ,CdⅡ,MnⅡ,CaⅡas center metal ions and imidazole,2,2-bipyridine,4,4-bipyridine,1,10-phenanthroline,6-nitrobenzimidazole as neutral ligands, and isophthalato,3-hydroxybenzoate,4-hydroxybenzoate, 2,5-dihydroxybenzoate, sulfonatoisophthalate, pyridine-3-sulfonate,2-carboxylate, 2-hydroxy-pyridine-3-carboxylate as anionic ligands. Their crystal structures have been determined by single X-ray diffraction method in this work.The new compounds synthesixed in this work are as below:1) Carboxyl and hydroxyl substituted benzoate complexes: [[Cd(C8H4O4)(H2O)3]·2.5H2O]n (Ⅰ) [Co(C7H5O3)2(C7H5N3O2)2(H2O)2]·2C7H5N3O2·2H2O (Ⅱ) [Cd(C7H5O4)2(C12H8N2)2]·1.25H2O (Ⅲ) Zn(C7H5O3)2(C10H8N2)(H2O) (Ⅳ) 2) Sulfonylisophthalate complexes: [Co(C8H4O7S)(C12H8N2)(H2O)3]·H2O (Ⅴ) (C10H9N2)2[Mn2(C10H8N2)3(H2O)8](C8H3O7S)2·C10H8N2·15H2O(Ⅵ) [CoNa4(C8H3O7S)2(H2O)12]n (Ⅶ) [Na4Ni(C8H3O7S)2(H2O)12]n (Ⅷ) [Mn(C10H8N2)(H2O)4][Mn2(C8H3O7S)2(C10H8N2)2(H2O)4]·4H2O (Ⅸ)3) Pyridylsulfonate complexes: [Cu(C5H4NO3S)2(H2O)2]n (Ⅹ) Ni(C5H4NO3S)2(H2O)4 (Ⅺ)4) Pyrimidulcarboxylate compounds: [Ca(C5H3N2O2)2]n (Ⅻ) [Co(C5H4N2O2)2(H2O)2]Cl2 (ⅩⅢ) Cu(C5H3N2O2)2 (ⅩⅣ) C5H5ON3 (ⅩⅤ)5) 2-Hydroxypyridyl-3-carboxyIate complexes: Co(C6H4NO3)2(C3H4N2)2 (ⅩⅥ) Ni(C6H4NO3)2(C3H4N2)2 (ⅩⅦ) {[MnNa(C6H4NO3)3]·H2O}n (ⅩⅧ)This dissertation focuses on four important supramolecular interactions. The aromaticπ-πstacking, CH...πinteraction, hydrogen bonding and Zn-O secondary bonding are mainly discussed. A Hartree-Fock (HF) ab initio calculations using STO-3G basis set with Gaussian03 program was performed in order to study Miliken charge transfer of aromatic ring. The results showed that the metal coordination, hetero-atoms and electron-withdrawing groups increasing the positive charge at the aromatic ring and effectingπ-πstacking. Main conclusions are as below.(1) Solution mixing method is more effective for prepare of single crystals without metal elemen(s). Hydrothermal method, solution reflux and solution mixing method are three complementary methods in synthesizing and cultivating metal complexes. The ratio of water and ethanol is essential for obtaining good single crystals of complex.(2) Metal coordination is benefic toπ-πstacking between aromatic rings. The introduction of electron-withdrawing groups on the aromatic ring is benefic toπ-πstacking interaction. The N-hetero atom(s) in the aromatic ring is also benefic toπ-πstacking. In this work, experimental results and the theoredical calculations well support the above conclusions.(3) Multi-cyclic compounds tend to formπ-πstacking than monocyclic compounds. Six-membered ring is easier than the five-membered ring to formπ-πstacking interaction.(4) Carboxyl, hydroxyl, sulfonic acid anions, uncoordinated N-hetero atoms are easy to form hydrogen bonding. Three oxygen atoms of sulfonate anion play the important role in forming hydrogen bonds.(5) CH...πinteractions is complementary toπ...πstacking interactions. Theπ...πstacking interactions exist in compounds (Ⅰ), (Ⅴ),(Ⅵ),(Ⅶ), (Ⅷ), (Ⅸ), (Ⅺ), (Ⅻ), (ⅩⅣ) and (ⅩⅤ), but no CH...πinteractions are found in these compounds, whereas CH...πstacking interactions exist in compounds (Ⅱ), (Ⅳ), (ⅩⅥ), (ⅩⅦ) but noπ-πstacking interaction exists in these compound. It seems that the role of CH...πandπ-πinteractions are complementary in the supramolecular structure.(6) Zn-0 secondary bonding widely exists in the crystal structure. Searching of CSD database (updates 2009.09), there are totally 544 ZnⅡcomplexes containing two carboxyl ligands. Within the total of 2448 Zn-0 distance in the 544 crystal structures, the Zn-0 distances raging from 2.20 A to 3.50A show a continuous distribution, which is different from the traditional point of view that Zn-O contact distance is either the sum of covalent radius or the sum of van der Waals radius. At the same time, the combination consideration of Zn-0 distance and corresponding bond angle is a good criterion for Zn-0 secondary bondings. When the C-Zn-0 angle is less than 108°, then 2.75 A for the Zn-O bond is the limit of secondary bonding.(7) The correct cell choice is importane for crystal structure determination. In the final D-Fourier map a unreasonable larger peak suggests the incorrect cell choice in the original determination for complex (IV). A cell resetting gave a reasonable crystal structure.