Supramolecular cobalt(II) complexes: syntheses,crystal structures and solvent effects

Two Co^II complexes, namely {[CoL(MeOH)(μ-OAc)]₂Co}·2MeCN·2MeOH (1) and {[CoL(EtOH)(μ-OAc)]₂Co}·3EtOH (2) (H₂L=3,3′-dimethoxy-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol), have been synthesized and characterized by X-ray crystallography. Both complexes contain octahedral coordination geometries, comprising three Co^II atoms, two deprotonated bisoxime L²⁻ units in which four μ-phenoxo oxygen atoms form two [CoL(X)] (X = MeOH or EtOH) units, two acetate ligands coordinated to three Co^II centers through Co–O–C–O–Co bridges, and coordinated and non-coordinated solvent. Both complexes exhibit 2D supramolecular networks through different intermolecular hydrogen-bonding interactions.     

Synthesis,crystal structures,and magnetic properties of three novel ferrocenecarboxylato-bridged lanthanide dimers

Three novel ferrocenecarboxylato-bridged lanthanide dimers [Gd2(mu 2-OOCFc)2(OOCFc)4(MeOH)2(H2O)2].2MeOH.2H2O (1) (Fc = (eta 5-C5H5)Fe(eta 5-C5H4)), [Nd2(mu 2-OOCFc)2(OOCFc)4(H2O)4].2MeOH.H2O (2), and [Y2(mu 2-OOCFc)2-(OOCFc)4(H2O)4].2MeOH (3) have been synthesized and characterized by single-crystal X-ray crystallography. In each complex, two Ln(III) (Ln = Gd, Nd, or Y) ions are bridged by two ferrocenecarboxylate anions as asymmetrically bridging ligands, leading to dimeric cores, [Ln2(mu 2-OOCFc)2]; each Ln(III) ion has an irregular polyhedral coordination environment with nine coordinated oxygen atoms derived from the ferrocenecarboxylate ligands and coordinated solvent molecules. In the solid-state structure of compound 1, [Gd2(mu 2-OOCFc)2(OOCFc)4(MeOH)2(H2O)2] groups are joined together by hydrogen bonds forming a two-dimensional network. Both compounds 2 and 3 show one-dimensional chain structures by hydrogen bonding; they are different from 1. Magnetic measurements show unexpected ferromagnetic coupling between the gadolinium(III) ions; the best fittings to the experimental magnetic susceptibilities gave J = 0.006 cm-1 and g = 2.0 for 1. The magnetic behavior for 2 was also studied in the temperature range of 1.8-300 K.     

Synthesis,crystal structures,and magnetic properties of three isomorphous helical coordination polymers

Three isomorphous coordination polymers of general formula {[M(H₂bna)·(DMF)₂·(H₂O)₂]·DMF}_n (M = Co for 1, Mn for 2, Ni for 3, respectively, where H₄bna = 2,2′-dihydroxy-[1,1′]-binaphthalene-3,3′-dicarboxylate) were synthesized under solvothermal conditions and characterized by FTIR, single crystal X-ray diffraction, thermogravimetric analysis, and X-ray power diffraction analysis. All three polymers crystallize in the same monoclinic space group P2₁/n. The complexes are assembled into 1D helical chains, and each adjacent helical chain of the same chirality is further connected to form a chiral layer by hydrogen bond interactions. The layers are packed in alternating left-(M) and right-handed (P) chirality arrays. Magnetic studies reveal the presence of antiferromagnetic coupling interactions in complexes 1 and 2.     

Solvothermal syntheses,crystal structures,and optical and thermal properties of transition metal selenidostannates

Four organic–inorganic hybrid selenidostannates, namely [H₂en][H₂dien][Fe(dien)₂]₂(Sn₂Se₆)₂ (1), [Fe(dien)₂]₂Sn₂Se₆ (2), [Fe(dien)₂]FeSnSe₄ (3), and [Mn(dien)₂]MnSnSe₄ (4) (en = ethylenediamine; dien = diethylenetriamine), were prepared in different solvents under solvothermal conditions. Complexes 1 and 2 consist of discrete [Sn₂Se₆]^4? and [Fe(dien)₂]²⁺ ions, as well as organic cations [H₂en]²⁺ and [H₂dien]²⁺ in 1. The dimeric [Sn₂Se₆]^4? anion is formed by two SnSe₄ tetrahedra via edge-sharing. Complexes 3 and 4 are composed of one-dimensional polyanions [TMSnSe ₄ ^2? ] _n plus [TM(dien)₂]²⁺ counter cations (TM = Fe, Mn). In the [TMSnSe ₄ ^2? ] _n anionic chain, the TM and Sn atoms are located at the same metal site with a ratio of 0.5/0.5. The TM_1/2Sn_1/2Se₄ tetrahedra are interlinked via edge-sharing, forming the heterometallic [TMSnSe ₄ ^2? ] _n polymeric anion. The [TM(dien)₂]²⁺ cations in 1–2 and 3–4 have u-fac and mer configurations, respectively. In all four crystal structures, the anions and cations are connected into extended structures via weak N–H···Se hydrogen bonds. The band gaps of complexes 1–4 calculated from the solid-state UV–vis diffuse reflectance spectra were at 2.58, 2.60, 2.21, and 2.25 eV, respectively. Thermogravimetric analyses show that complex 1 decomposes in three steps, while complexes 2–4 each decompose in one step.     

CdWO4 polymorphs: Selective preparation, electronic structures, and photocatalytic activities

This work explored the selective synthesis of polymorphs of CdWO₄ in either tetragonal or monoclinic phase by optimizing the experimental parameters. Systematic characterization indicated that both polymorphs possessed similar spherical morphologies but different structural building blocks. Electronic structures calculations for both polymorphs demonstrated the same constructions of conduction band or valence band, while the conduction band widths of both polymorphs were quite different. Both CdWO₄ polymorphs exhibited good photocatalytic activity for degradation of methyl orange under UV light irradiation. When comparing to some other well-known tungstate oxide materials, the photocatalytic activity was found to follow such a consequence, monoclinic CdWO₄≈monoclinic ZnWO₄>tetragonal CdWO₄>tetragonal CaWO₄. The specific photocatalytic activity of monoclinic CdWO₄ was even higher than that of commercial TiO₂ photocatalyst (Degussa P25). The increased activity from the tetragonal CdWO₄ to the monoclinic was consistent with the trend of the decreased symmetry, and this could be explained in terms of the geometric structures and electronic structures for both polymorphs.     

Synthesis,crystal structures,and luminescent properties of three cluster-based heterometallic and monometallic compounds

Two heterometallic cluster compounds and one monometallic cluster compound, namely [Ni₉Co₆(PMIDA)₆(BTC)₂(H₂O)₁₂]·6H₂O (1), [Co₁₃Zn₂(PMIDA)₆(H₂O)₁₈]·6NO₃·15H₂O (2), and [Fe₁₅(PMIDA)₆(BTC)₂(H₂O)₂₂]·38H₂O (3), have been obtained under hydrothermal conditions using N-(phosphonomethyl)imino-diacetic acid (H₄PMIDA) and 1,3,5-benzenetricarboxylate acid (H₃BTC) as ligands, and structurally characterized by X-ray crystallography. Compound 1 exhibits a 3D open framework constructed from [Ni₉Co₆(PMIDA)₆(H₂O)₁₂]⁶⁺ heteronuclear clusters and BTC^3? ligands. Compounds 2 and 3 are both zero-dimensional polynuclear clusters, further extended into 3D supramolecular structures via hydrogen-bonding interactions. However, there are some differences in their crystal structures; compound 2 features an isolated spherical heteronuclear cation cluster based on PMIDA^4? ligands, such that the NO₃ ^? anions only balance the charge, whereas compound 3 is characterized as a neutral monometallic cluster incorporating two different types of organic acid ligands, namely PMIDA^4? and BTC^3?, and the two BTC^3? ligands exhibit regular distribution in each cluster. The luminescence properties of all three compounds have been investigated at room temperature.     

Heterometallic copper(Ⅱ) vanadates: synthesis,crystal structures and third-order nonlinear optical properties

Three polymeric heterometallic clusters with 1D, 2D, and 3D frameworks, constructed from a cyclic vanadate {V4O12}4-building block and three geometric constraint ligands, were synthesized by a one-pot self-assembly reaction. Z-scan experiments demonstrated that all the three cluster polymers have large hyperpolarizability γ values. TD-DFT calculations afforded insight into the electronic transitions and spectral characterization of these novel NLO molecular materials.     

Synthesis,crystal structures,and third-order nonlinear optical properties of a series of ferrocenyl organometallics

Three novel ferrocenyl complexes [Zn(4-PFA)(2)(NO(3))(2)](H(2)O) (1), [Hg(2)(OAc)(4)(4-BPFA)(2)](CH(3)OH) (2), and [Cd(2)(OAc)(4)(4-BPFA)(2)] (3) (4-PFA = [(4-pyridylamino)carbonyl]ferrocene, 4-BPFA = 1,1'-bis[(4-pyridylamino)carbonyl]ferrocene) were prepared, and complexes 1 and 2 were structurally characterized by means of X-ray single-crystal diffraction. In complex 1, the zinc(II) atom is coordinated at a distorted tetrahedral environment by two nitrogen atoms from two 4-PFA moieties and two oxygen atoms from two nitrate anions; [Zn(4-PFA)(2)(NO(3))(2)] units are linked by hydrogen bonds N-H.O and O-H.O forming one-dimensional chains. Complex 2 is a tetranuclear macrocycle compound consisting of two 4-BPFA moieties and two Hg atoms; [Hg(2)(OAc)(4)(4-BPFA)(2)] units form 1-D chains by hydrogen bonds N-H.O as complex 1. Some complexes with 1,1'-bisubstituted pyridine-containing ferrocene ligands have been described, but their crystal data are limited. Compound 2 is the first example of a macrocyclic pyridine-containing ferrocenyl complex. The third-order nonlinear optical (NLO) properties of 4-PFA, 4-BPFA, and complexes 1-3 were determined by Z-scan techniques. The results indicate that all the compounds exhibit strong self-focusing effect. The hyperpolarizability gamma values are calculated to be in the range 1.51 x 10(-)(28) to 3.12 x 10(-)(28) esu. The gamma values are nearly twice as large for complexes 1-3 as for their individual ligands, showing that the optical nonlinearity of the complexes is dominated by the ligands.     

Studies on crystal growth, vibrational and optical properties of organic nonlinear optical crystal: p-aminoazobenzene

p-Aminoazobenzene (p-AAZB), an organic nonlinear optical (NLO) crystal having good optical quality has been grown by slow evaporation solution technique using ethanol as a solvent. Solubility studies were performed at different temperatures. The structural characterization of the grown crystals was carried out by X-ray diffraction. Group theoretical analysis was carried out to calculate the number of modes of vibration. The lowering of the wave numbers of azo group suggests the existence of strong intermolecular N-H...H hydrogen bonding. This has been analysed based on the vibrational spectral features. Optical absorption studies show the effective transmission in the entire UV-vis region. The second harmonic generation results show the suitability of this material for NLO applications.     

Two new copper azido polymorphs: structures, magnetic properties, and effects of "noninnocent" reagents in hydrothermal methods

Two new 3D copper(II) azido isomers, [Cu(N3)(nic)]infinity (1 and 2) (nic = nicotinate), have been synthesized and characterized. To the best of our knowledge, 1 is the first metal azido complex showing rutile-type topology, while 2 is a chiral compound obtained by spontaneous resolution upon crystallization.     

Cyanocomplexes with one-dimensional structures: preparations,crystal structures and magnetic properties

The review surveys the preparation methods, crystallochemistry and magnetic properties of one-dimensional cyanocomplexes. Their preparation methods are mainly based on reactions in solutions containing suitable building blocks as precursors of the polymeric structure. The analysis of published data on crystal structures is given, as the knowledge of the crystal structure is essential for the study of magneto-structural correlation. Published data on magnetic properties are discussed along with the methods used for the study of magnetic properties.     

Cyclic triureas--synthesis, crystal structures and properties

The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been studied by 1H NMR. Complexation constants for chloride, bromide and acetate have been measured for all trimers by UV spectrophotometry. Molecular dynamics simulations have been carried out to determine the conformation of the free receptors in chloroform and acetonitrile. They show that in chloroform, intramolecular hydrogen bonding occasionally facilitated by trans-->cis isomerisation of an amide bond dominates the conformation of the macrocycles while in acetonitrile (the solvent used for complexation measurements), the ligating urea NH protons are properly arranged for the complexation of anions, however, their strong solvation is counteractive to the complexation.     

Argon solvent effects on optical properties of silver metal clusters

Argon gas at a high pressure (～80 bar) has been expanded using a miniaturized pulsed valve at room temperature, producing a supersonic beam of cold, large argon droplets. Atoms of silver are subsequently embedded into the droplet using the pick-up technique. The resulting Ag(n)Ar(droplet) distribution was analyzed using multiphoton laser ionization time-of-flight mass spectrometry. Besides bare metal clusters, snowballs of silver monomers and dimers encapsulated in up to 50 argon atoms have been observed. The influence of the solvent on the optical absorption of the solute was studied for embedded Ag(8) using resonant two-photon ionization in the ultraviolet. A redshift and broadening of the Ag(8)Ar(droplet) optical spectrum compared to that measured in pure [Federmann et al., Eur. Phys. J. D 1999, 9, 11] and Ar-doped helium droplets [Diederich et al., J. Chem. Phys.2002, 116, 3263] was observed, which is attributed to the interaction with the larger Ar matrix environment.     

Microsolvation effects on the optical properties of crystal violet

We present a joint experimental and theoretical study of the photoabsorption and photodissociation behavior of crystal violet, that is, the tris[p-(dimethylamino)phenyl]methyl cation. The photodissociation spectra of isolated and microsolvated crystal violet have been measured. A single band is observed for the bare cation. This is in good agreement with the calculated vibronic absorption spectrum based on time-dependent density functional theory calculations. The interaction of crystal violet with a single water molecule shifts and broadens the photodissociation spectrum, so that it approaches the spectrum obtained in solution. Theoretical calculations of the structure of the complex suggest that the shift in the absorption spectrum originates from a water molecule bonding with the central carbon atom of crystal violet.     

The effects of auxiliary ligands on the synthesis,crystal structures and properties of three complexes with a substituted pyridazine ligand

Abstract  Three new complexes, [Co(L)₂(SCN)₂] (1), [Co₂(L)₄(μ-N₃)₂](ClO₄)₂(H₂O)_1.5 (2), and [Ni(L)₃](ClO₄)₂(CH₃OH)₂ (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Single crystal X-ray analyses show that all three complexes crystallize in the monoclinic crystal system. In complex (1), the Co(II) atom is in a distorted octahedral environment consisting of four nitrogen atoms from two ligands and two nitrogen atoms of SCN⁻, which is further extended into a 1D chain by intermolecular hydrogen bonds. Two Co(II) atoms in complex (2) are linked by two azide anions in a μ-1,1 mode to make a binuclear structure. Without any auxiliary ligand, the Ni(II) atom in complex (3) adopts a distorted octahedral geometry involving six nitrogen atoms from three ligands. The electronic absorption spectra of the title compounds are discussed as well. The effects of auxiliary ligands on the structures and properties of the title complexes have been studied and discussed. Graphical Abstract  Three new complexes, [Co(L)₂(SCN)₂] (1), [Co₂(L)₄(μ-N₃)₂](ClO₄)(H₂O)_1.5 (2) and [Ni(L)₃](ClO₄)₂(CH₃OH)₂ (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Complexes (1) and (3) are mononuclear compounds, which are different from the binuclear complex (2). Auxiliary ligands are the main reasons that results in the different structures of the title complexes and their different fungicidal activities. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis,crystal structures and magnetic and electrochemiluminescence properties of three manganese(II) complexes

Three novel complexes, namely, penta‐μ‐acetato‐bis(μ₂‐2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)‐μ‐formato‐tetramanganese(II), [Mn₄(C₁₃H₁₁ClN₃O₂)₂(C₂H₃O₂)_5.168(CHO₂)_0.832], 1 , hexa‐μ₂‐acetato‐bis(μ₂‐2‐{[2‐(6‐bromopyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)tetramanganese(II), [Mn₄(C₁₃H₁₁BrN₃O₂)₂(C₂H₃O₂)₆], 2 , and catena‐poly[[μ₂‐acetato‐acetatoaqua(μ₂‐2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolato)dimanganese(II)]‐μ₂‐acetato], [Mn₂(C₁₃H₁₁ClN₃O₂)(C₂H₃O₂)₃(H₂O)]_n, 3 , have been synthesized using solvothermal methods. Complexes 1 – 3 were characterized by IR spectroscopy, elemental analysis and single‐crystal X‐ray diffraction. Complexes 1 and 2 are tetranuclear manganese clusters, while complex 3 has a one‐dimensional network based on tetranuclear Mn₄(L¹)₂(CH₃COO)₆(H₂O)₂ building units (L¹ is 2‐{[2‐(6‐chloropyridin‐2‐yl)hydrazinylidene]methyl}‐6‐methoxyphenolate). Magnetic studies reveal that complexes 1 – 3 display dominant antiferromagnetic interactions between Mn^II ions through μ₂‐O bridges. In addition, 1 – 3 also display favourable electrochemiluminescence (ECL) properties.