Syntheses, Structures, and Fluorescent Properties of 2-(1H-Imidazol-2-yl)phenols and Their Neutral Zn(II) Complexes

Abstract

A series of 2-(imidazole-2-yl)phenol ligands L1-L6 with the general composition 4-R(4)-5-R(3)-6-R(2)-2-(4,5-R(1),R(1)-1H-imidazole-2-yl)phenol (L1: R(1) = C(2)H(5), R(2) = R(3) = R(4) = H; L2: R(1) = C(6)H(5), R(2) = R(3) = R(4) = H; L3: R(1) = C(6)H(5), R(3) = OCH(3), R(2) = R(4) = H; L4: R(1) = C(6)H(5), R(4) = OCH(3), R(2) = R(3) = H; L5: R(1) = C(6)H(5), R(3) = H, R(2) = R(4) = CH(3); L6: R(1) = C(6)H(5), R(3) = H, R(2) = R(4) = t-Bu) and L7 (2,4-di-tert-butyl-6-(1H-phenanthro[9,10-d]imidazol-2-yl)phenol) and their neutral Zn(II) complexes (Z1-Z7) were synthesized and characterized by spectroscopic and elemental analyses. Molecular structures of L1, L5, Z1, and Z2 were confirmed by single-crystal X-ray diffraction. L1 crystallized in the monoclinic Cc space group, while L5, Z1, and Z2 all crystallized in the triclinic P1 space group. One-dimensional arrays based on continuous pi-pi stacking interactions and hydrogen bonding were observed for L1 and Z1, while L5 existed as discrete dimeric stack units. Z2 formed hydrogen-bonded 1D network structures but was completely devoid of pi-pi stacking interactions. Emission processes were found to be more dependent on the substituents on phenol as well as condensed media. In contrast to general conclusions on closely related systems in the literature, significant photorelaxation from the excited enol state was observed in the cases of L1 in methanol and L4 in both THF and methanol. Therefore, there exists a certain unusual hindering factor to keto-enol phototautomerism in the ligand-solvent systems. The sensing property of zinc(II) complexes was explored regarding the effects of substituents in their ligands. It was observed that coordination to the zinc(II) ion led to emission quenching for L1 and L2 while causing an enhancement of fluorescent intensity for L3, L4, L5, and L6. A linear relationship was observed between the emission intensity and the concentration of the zinc ion at the 10(-8) M level. Compared to other zinc compounds in this work, fluorescence enhancement in Z3 and Z4 showed that the methoxyl substituent is favorable for fluorescent enhancement.

Synthesis and Antimicrobial Activity of 2-Trifluoroacetonylbenzoxazole Ligands and Their Metal Complexes

“…1 [29][30][31][32][33][34][35][36][37][38][39] In the Zn(II) complex 2b, the geometry at the Zn(II) center can be best described as a distorted tetrahedron in which two benzoxazole-2-chlorodifluoroacetonate (1b) ligands are placed in a similar disposition about the zinc center. [29][30][31] One coordination plane (N-O-Zn) in 2b is approximately perpendicular to the other with a dihedral angle of 89.2°. The molecular structure of 2b was incorporated with hexane molecule.…”

Towards the Development of Fiber-Based Oxidovanadium(IV) Catalysts for the Oxidation of Thioanisole

“…All substituted 2-(4,5-diphenyl-1H-imidazole-2-yl)phenol derivatives were prepared according to a literature procedure [14]. 13 …”

“…The use of vanadium catalysts for the oxidation of sulfides has attracted much interest in this regard. Both oxidovanadium(IV) [12] and dioxidovanadium(V) [13] complexes have been shown to facilitate the oxidation of not only sulfides but several organic substrates including alkanes and alkenes [14].…”

Synthesis, crystal structure, and luminescent properties of metal complexes bearing 2,6-pyridine-diacylhydrazide ligands: supramolecular assemblies via intermolecular interactions

“…The process of the self-assembly of a supramolecular framework is based on the extension of individual molecules by noncovalent or weak covalent interactions, including Van der Waals, electrostatic and hydrophobic interactions, hydrogen bonds, as well as p-p and ion-p stacking [11][12][13][14][15][16][17][18][19][20][21]. Among these, hydrogen bonding and p-p stacking interactions have been considered to play active roles in the formation of ordered supramolecular chains, layers, and three-dimensional frameworks, the research on which is of great interest for the development of supramolecular chemistry [22][23][24][25][26][27][28][29].…”