Deng-Ke Cao

Chiral-layered metal phosphonate formed via spontaneous resolution showing dehydration-induced antiferromagnetic to ferromagnetic transformation.

Metal phosphonates M (II){(2-C 5H 4N)CH 2NHCH 2PO 3} (H 2O) [M = Mn ( 1), Cd ( 2)] with chiral-layered structures are obtained by spontaneous resolution using achiral starting materials. The magnetic behavior of 1 is transformed from antiferromagnetic to ferromagnetic upon dehydration.

Kinetics of Solid State Photodimerization of 1,4-Dimethyl-2-pyridinone in its Molecular Compound

The [4 + 4] photodimerization of 1,4-dimethyl-2-pyridinone (A) in its molecular compound with 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol (I) was investigated by irradiation of a single crystal of the compound. The conversion to the product in a single-crystal to single-crystal transformation enabled the determination of its crystal structure after each exposure cycle of 10-20 min with a pulsed 355 nm laser light. The unit cell changes as a function of the conversion were monitored and showed monotonic changes. The kinetics of the reaction was studied at two different temperatures (230 and 280 K) and revealed a sigmoidal behavior that could be explained by the JMAK model for crystal growth with a mechanism that is intermediate between random distribution of products in the crystal and the existence of growing nuclei. The Arrhenius plot provided calculated activation energy of 32.5 kJ/mol.

Synthesis and characterization of two metal phosphonates with 3D structures: CuI2CuII[(3-C5H4N)CH(OH)PO3]2 and Zn[(3-C5H4N)CH(OH)PO3]

Two novel phosphonate compounds, CuI2CuII[(3-C5H4N)CH(OH)PO3]2 (1) and Zn[(3-C5H4N)CH(OH)PO3] (2), have been synthesized by solvothermal reactions of the corresponding metal salts with [hydroxy(3-pyridyl)methyl]phosphonic acid. Compound 1 contains inorganic chains made up of CuIIO4 planes and CPO3 tetrahedra through corner sharing. These chains are connected by CuION units through pyridine rings, forming a 3D open framework structure. Compound 2 adopts a new type of pillared layered structure. The inorganic layer contains 8- and 16-membered rings made up of ZnO3N and CPO3 tetrahedra. Pyridine rings are fixed between the inorganic layers through covalent bonds. The magnetic study shows that weak ferromagnetic interactions are mediated between magnetic centers in compound 1.

Mononuclear lanthanide complexes incorporating an anthracene group: structural modification, slow magnetic relaxation and multicomponent fluorescence emissions in Dy compounds

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.

Cyclometalated Ir(III) complexes containing quinoline–benzimidazole-based N^N ancillary ligands: structural and luminescence modulation by varying the substituent groups or the protonation/deprotonation state of imidazole units

Cyclometalated Ir(iii) complexes [Ir(dfppy)2(qbiH)](PF6) (1), [Ir(dfppy)2(qbim)](PF6)·H2O (2), [Ir(dfppy)2(qbio)](PF6) (3) and [Ir(dfppy)2(qbi)] (4) have been designed and prepared, in which the N^N ligands qbiH, qbim and qbio incorporate different substituent groups R on their imidazole units (H atom, CH3 group and n-C8H17 group, respectively) in order to explore the influence of the substituent groups R and the protonation/deprotonation state of imidazole units in these Ir(iii) complexes on their structures and luminescence behaviors. Crystal structures indicate that an {Ir(dfppy)2}+ unit is coordinated by neutral ligands qbiH in 1, qbim in 2 and qbio in 3, while a qbi- anion in 4. These Ir(iii) complexes show clearly different molecular stacking modes. In compound 1, neighboring [Ir(dfppy)2(qbiH)]+ cations are linked into a supramolecular chain through ππ stacking interactions between adjacent dfppy-/qbiH ligands. In 2 and 4, two neighboring iridium complex units connect each other through ππ stacking interactions between dfppy- ligands in the former, while between qbi- ligands in the latter, forming supramolecular dimers. Compared to 1, 2 and 4, compound 3 only exhibits intermolecular van der Waals interactions. At room temperature, these Ir(iii) complexes in CH2Cl2 reveal phosphorescence with a mixing of 3MLCT and 3LC characters, emissions at 558 and 585 nm for 1, 572 (or 573) and 600 nm for 2 and 3, and 546 nm for 4. Compared to 1-3, compound 4 displays relatively weak luminescence intensity. Interestingly, upon addition of NEt3/TFA, both 1 and 4 in CH2Cl2 can switch their luminescence between strong emission at 558 nm and weak emission at 546 nm, due to their acid-/base-induced structural interconversion between the protonation state and the deprotonation state of the qbiH ligand. The emissions of 1-4 in the solid state reveal different degrees of the red shift compared to their corresponding emissions in CH2Cl2, the broad emission bands at 542, 572 and 611 nm for 1, 553, 581 and 612 nm for 2, 544, 578 and 630 nm for 3, and 595 and 633 nm for 4. Based on the crystal structures of 1-4, this work discusses the luminescence modulation of these Ir(iii) complexes by varying their substituent groups or the protonation/deprotonation state of the imidazole units.

Phosphonates containing 8-hydroxyquinoline moiety and their metal complexes: structures, fluorescent and magnetic properties

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.

Two heteroleptic Ir(III)–bisthienylethene compounds: syntheses, structures and aggregation-induced luminescence

A new bisthienylethene 2-(2-hydroxynaphthyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (hnbdtiH) has been synthesized and applied for the coordination-assembly generation of two heteroleptic complexes [Ir(dfppy)2(hnbdti)]·2CH3OH (1) and [Ir(ppy)2(hnbdti)]·CH3OH (2) [dfppyH = 2-(2,4-difluorophenyl)-pyridine, ppyH = 2-phenyl-pyridine]. In the crystal structure of hnbdtiH, neighboring molecules are linked into a helical chain through N–H⋯π interactions between imidazole and naphthol rings. In 1 and 2, the {Ir(dfppy)2}+ or {Ir(ppy)2}+ unit is chelated by a hnbdti− ligand using both N and O binding sites, and the intramolecular aromatic stacking interactions are formed between the thiophene ring and the 2,4-difluorophenyl/phenyl group. The crystal structures of 1 and 2 indicate that neighboring molecules are connected by CH3OH molecules through hydrogen bond interactions, forming the [Ir⋯(CH3OH)4⋯Ir] dimer in the former, and the [Ir⋯(CH3OH)2⋯Ir] dimer in the latter. These dimers in 1 pack together through the intermolecular aromatic stacking interactions, while there are only van der Waals interactions in 2, resulting in their distinct luminescence behavior. At room temperature, 1 exhibits aggregation-induced phosphorescence emission. In contrast, 2 is almost non-luminescent both in solution and in the solid state. Compared with 1 and 2, free ligand hnbdtiH shows fluorescence both in CH2Cl2 solution and in the solid state. Moreover, no photochromism has been observed in hnbdtiH, 1 and 2.

A mononuclear Dy(III) complex incorporating the dithienylethene unit: crystalline-phase photochromism, magnetic and luminescent properties

A new dithienylethene compound 2-(4-diethylphosphonophenyl)-4,5-bis(2,5-dimethyl(3-thienyl))-1H-imidazole (dbi) has been synthesized and applied for the coordination-assembly generation of a mononuclear complex [Dy(hfac)3(dbi)2]·CH3OH (1) (hfac = hexafluoroacetylacetonate), in which dbi ligands coordinate to Dy(III) ion through phosphoryl oxygen atoms. In the crystal structure of dbi, each molecule shows a parallel conformation, and neighboring molecules are linked into an interesting helical chain through hydrogen bonds. In contrast, each dbi ligand in 1 exhibits a photoactive antiparallel conformation, thus resulting in crystalline-phase photochromism (CPP) behavior of 1. Before and after CPP reaction, 1 shows different magnetic and luminescence properties. After irradiation with 365 nm light, the shape of the χMT vs. T plot revealed drastic changes, and field-induced χM′′ peaks were observed. Compound 1 exhibits ligand- and Dy(III)-centered fluorescence emissions. The irradiation with 365 nm light resulted in the red shift of dbi-centered emissions, and the decrease in intensity of Dy(III)-centered emission.

Cobalt and copper phosphinates based on N-(phosphinomethyl)iminodiacetic acid: supramolecular layered structures and magnetic properties

Reactions of N-(phosphinomethyl)iminodiacetic acid (H3L) and cobalt or copper salts in aqueous solutions result in two new metal phosphinates, [Co(H2O)6][Co2L2]·2H2O (1) and [Cu(H2O)4][Cu2L2] (2). Both compounds exhibit different supramolecular layered structures, which result from the assembly of cationic and anionic moieties through hydrogen bond interactions. In 1, {Co2O2} dimers are linked through O–P–O units into a {[Co2L2]}n2n− double chain and [Co(H2O)6]2+ serve as a counterion. Compound 2 contains two kinds of chain-like moieties, i.e. {[Cu2L2]}n2n− and {[Cu(H2O)4]}n2n+. The former is made up of corner-sharing {CuO4N} square pyramids and {PHO2C} tetrahedra and the latter is formed through edge-sharing connections of {CuO6} octahedra. Magnetic studies reveal a dominant ferromagnetic interaction mediated between the magnetic centers in 1, while antiferromagnetic interactions are dominant in 2.

Formation of different photodimers of isoquinolinone by irradiation of solid molecular compounds

[4 + 4] Photodimerization of isoquinolin-3(2H)-one (isoquinolinone) (1) may yield 12 different isomers depending on the relative geometry of the two monomers prior to the reaction. Irradiation of the solid neat compound shows that of all possible dimers only the dimer between the two hetero-rings having an inversion center is produced. On the other hand, exposure to UV light of solid molecular compounds composed of isoquinolinone as the guest molecule and different host molecules shows to produce few other isomers of the dimer. The use of different host molecules affects the packing of the molecules in the crystal. As a result, the relative geometries between two monomer molecules are varied enabling photochemical dimerization to yield different isomers. When 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol (I) is used as the host molecule, two polymorphic forms of the molecular compound are obtained. Irradiation of single-crystal of the two polymorphs yields a mixture of isomers of the dimer. When the host molecule is cyclohexanol-1,2,4,5-tetracarboxylic acid (II) three isomers are expected, and when the host molecule is 1,3-benzenediol (III) a single isomer is formed which is identical to that obtained from the neat isoquinolinone.