RESUMO
Based on two new bisthienylethenes containing N,O-donor binding sites, 2-(2-hydroxy-5-bromo-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (BrLH) and 2-(2-hydroxy-5-diethylphosphono-phenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (PLH), multifunctional mononuclear complexes Co(BrL)2·3CH3OH (1) and Co(PL)2·2CH3OH (2) have been synthesized and characterized by crystallographic analysis. In the molecular structures of 1 and 2, the Co(II) ion adopts a distorted tetrahedral coordination geometry, and is coordinated by two nonequivalent bisthienylethene molecules (BrL− in 1, PL− in 2), showing non-photoactive parallel and photoactive antiparallel conformations, respectively. Compounds 1 and 2 show a distinct distortion of Co(II) coordination geometry, with bond angles of NCoN = 112.71(12)° and OCoO = 99.87(11)° for 1 and NCoN = 119.93(12)° and OCoO = 107.31(13)° for 2. Thus, 1 and 2 revealed different magnetic behaviors, which are demonstrated by the χMT vs. T plots, and the frequency dependence of the χ'M and χ''M signals at low temperature. Besides the field-induced slow magnetic relaxation, both 1 and 2 also showed photochromic behavior. Upon irradiation with 360 nm light for 1 and 343 nm light for 2, their CH2Cl2CH3CN solutions could change color from being nearly colorless to blue purple. It was demonstrated that the substituent groups of Br atom and PO(OEt)2 in 1 and 2, respectively, could significantly influence their crystal structures, magnetic relaxations and photochromic properties.
RESUMO
Mononuclear complex Co(hpbdti)2·3CH3OH (1) was synthesized [hpbdtiH = 2-(2-hydroxyphenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole], showing multiple-step field-induced slow magnetic relaxation behaviors, and photochromic properties in CH2Cl2-CH3CN solution.
RESUMO
Four mononuclear lanthanide complexes, [Ln(hfac)3(depma)(H2O)] [Ln(III) = Dy (1), Gd (2)], [Dy(hfac)3(depma)2]2·H2O (3) and [Gd(hfac)3(depma)2]·2H2O (4), have been obtained (hfac = hexafluoroacetylacetonate, depma = 9-diethylphosphonomethyl anthracene) by using one (for 1 and 2) or two (for 3 and 4) depma molecules to substitute coordination water molecules of Ln(hfac)3(H2O)2. It was found that the number of introduced depma ligands can modify the coordination geometry of Ln(iii) ions, showing a distorted biscapped triangular prism geometry in isostructural 1 and 2 and a distorted square-antiprismatic geometry in 3 and 4. Magnetic studies reveal that both 1 and 3 show field-induced slow magnetic relaxation under the applied dc field of 1000 Oe. The solid-state fluorescence measurements indicate the presence of multicomponent emissions in 1 and 3, including ligand-centered (LC) emissions from hfac and depma, and yellow emission from Dy(III) ions and only ligand-centered (LC) emissions in 2 and 4.
RESUMO
Two kinds of solid-state structures of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3) have been obtained, namely 1·HCl·H2O and 1·H2O, involving different hydrogen bonds and/or aromatic stacking interactions. As a derivative of 5pm8hqH3, 5-phosphonomethyl-8-(carboxymethoxy)quinoline (5pm8cmoqH3) was synthesized. Based on 5pm8hqH3 and 5pm8cmoqH3, three new metal phosphonates have been hydrothermally prepared, including Zn(5pm8hqH)(H2O)·H2O (2), Cu(5pm8cmoqH)·2H2O (3) and Fe(5pm8cmoqH) (4), exhibiting layered structures for 2 and 4, and a three-dimensional open framework for 3. The 8-hydroxyquinoline moieties in 1·H2O and 2-4 exhibit three kinds of interesting aromatic stacking modes, including pyridine ring-pyridine ring stacking between a pair of moieties, double benzene ring-pyridine ring stacking between a pair of moieties and alternating benzene ring-benzene ring and pyridine ring-pyridine ring stacking among a number of moieties in the layered structure. The solid-state fluorescence measurements indicate the emissions of 1·HCl·H2O and 1·H2O are significantly different due to their distinct packing structures. Compound 2 exhibits both ligand-centered (LC) and ligand-to-metal charge transition (LMCT) emissions. Magnetic studies reveal dominant antiferromagnetic interactions in 3 and 4.