Crystal engineering of Co(II), Ni(II), CU(II) and Zn(II) coordination complexes with imidazole derivatives as ligands

The main target of this thesis was the crystal engineering studies of transition metal complexes of CoII, NiII, CuII and ZnII with substituted imidazoles as ligands. Crystal engineering may be regarded as the solid-state branch of supramolecular chemistry. Supramolecular chemistry is one of the most popular and rapidly developing areas of experimental chemistry. It may be defined as the chemistry of weak intermolecular forces and focuses on the structure and function of chemical systems with higher complexity (supermolecules), that result from the association of two or more discrete chemical species (molecules, ions) held together by weak (and reversible) intermolecular forces (e.g. π-π interactions, hydrogen bonds, hydrophobic interactions, van der Waals forces, dipole-dipole interactions, metal-ligand coordination bonds etc). [...]Βασικός στόχος της παρούσης Διατριβής ήταν η μελέτη της κρυσταλλικής μηχανικής συμπλόκων ενώσεων των μεταβατικών μετάλλων CoII, NiII, CuII και ZnII με ιμιδαζολικά παράγωγα ως υποκαταστάτες. Η κρυσταλλική μηχανική μπορεί να θεωρηθεί ως ο κλάδος της υπερμοριακής χημείας στη στερεά κατάσταση. Η υπερμοριακή χημεία (supramolecular chemistry) είναι μια από τις πλέον δημοφιλείς και γρήγορα αναπτυσσόμενες περιοχές της πειραματικής χημείας. Χαρακτηρίζεται ως η χημεία των ασθενών διαμοριακών δυνάμεων και εστιάζει στη δομή και λειτουργία χημικών συστημάτων με υψηλότερη πολυπλοκότητα (υπερμόρια) που προκύπτουν από το συνδυασμό δύο ή περισσοτέρων διακριτών χημικών ειδών (μορίων, ιόντων) και συγκρατούνται με ασθενείς (και αντιστρεπτές) διαμοριακές δυνάμεις (π.χ. αλληλεπιδράσεις π-π, δεσμούς υδρογόνου, υδρόφοβες αλληλεπιδράσεις, δυνάμεις van der Waals, αλληλεπιδράσεις διπόλου-διπόλου, δεσμούς ένταξης μετάλλου-υποκαταστάτη κλπ). [...

Zinc(II) and Nickel(II) Benzoate Complexes from the Use of 1-methyl-4,5-diphenylimidazole

Two new complexes, [Zn(O2CPh)2(L)2]⋅2MeOH  (⋅2MeOH) and [Ni2(O2CPh))4(L)2]⋅2MeCN  (⋅2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the MII/X−/L[MII=Co,Ni,Cu,Zn; X−=Cl−,Br−,I−,NCS−,NO−3,N−3,PhCO−2; L=1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex ⋅2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N2O2 coordination environment. Complex ⋅2MeCN exhibits a dinuclear paddle-wheel structure; each NiII has a square pyramidal NiNO4 chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of ⋅2MeOH is stabilized by intramolecular - interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX2L2]

A Systematic Evaluation of the Interplay of Weak and Strong Supramolecular Interactions in a Series of Co(II) and Zn(II) Complexes Tuned by Ligand Modification

A systematic investigation on a designed series of 21 transition metal complexes has been carried out with the intention to explore and assess the relative strength and the way in which intermolecular interactions, namely, weak and strong hydrogen-bonding and π–π interactions, cooperate and direct molecular association during crystallization. The complexes were prepared using the general M^II/X^–/L or HL′ (M^II = Co^II, Zn^II; X^– = Cl^–, Br^–, I^–, NO₃^–, NO₂^–, ClO₄^–; L = 1-methyl-4,5-diphenylimidazole; and HL′ = 4,5-diphenylimidazole) reaction system and were characterized by single-crystal X-ray crystallography. Although the two ligands are structurally similar, the crystal packing organization of their complexes is markedly different. In structures with L, the 3D assembly is based only on weak C–H···X, C–H···π, and intramolecular π···π stacking interactions, whereas in those with HL′, it is the recurring N–H···X motifs that clearly dominate and guide the molecular self-assembly. The formation of such synthons has been activated by choosing appropriate anions X, acting as terminal ligands or counterions. In parallel, the conformational flexibility of the two ligands serves a dual purpose: (i) L contributes to the stabilization of complexes via intramolecular π···π stacking interactions, and (ii) HL′ facilitates the synthon formation by adopting appropriate conformations, even at the expenses of the stabilizing intramolecular π···π stacking