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We report a phosphine-directed ruthenium-catalyzed C8-selective alkylation of naphthalenes with alkenes. This protocol provides straightforward access to a large library of electron-rich C8-alkyl substituent 1-naphthphosphines, which outperformed common commercial phosphines and their precursors in the Pd-catalyzed Suzuki–Miyaura coupling of aryl bromides with alkylboronic acid. [ABSTRACT FROM AUTHOR]

Different surface planes of various types of titanium dioxide (TiO2) crystals have diverse catalysis effects on the splitting of H2O and H2 and the electronic structures of the formed hydroxylated TiO2 vary significantly. A series of sixteen types of hydroxylated TiO2 surfaces containing two types of hydroxyls (OH1 and OH2) on four kinds of low index surfaces [(001), (100), (101), and (110)] of two types of crystals [anatase (A) and rutile (R)] are studied using first-principles density functional theory calculations. The catalyzed splitting of H2O and H2 on the eight low index surfaces is compared using Gibbs free energy. The geometries and electronic structures including the total and partial density of states and the charge density distribution of the sixteen hydroxylated surfaces are systematically described. The electronic structures of R-101, R-001, A-110, A-100, and A-001 surfaces are more significantly influenced by hydroxylation than other surfaces and the effects of OH2 are larger than those of OH1. In particular, the band gap values decrease and a new electronic energy state appears in R-001-OH2 and A-100-OH2. A new electronic state appears in the middle of the bands of R-101 and A-110 surfaces upon hydroxylation. The electron spin balance at the edge of the conduction band minimum of A-001-OH2 is disturbed. This research can provide theoretical guidance for experimental researchers to design surface hydroxylated TiO2 materials with tunable electronic structures and high catalytic performance. [ABSTRACT FROM AUTHOR]

Extending new families of ABX3-type three-dimensional (3D) molecular perovskites based on diverse X-site molecular ligands is of interest in designing advanced hybrid materials for wide usage. Being a pseudo-halogen ligand, the thiocyanate anion is expected as an X-site bridge to construct 3D molecular perovskites, but has only yielded two pure inorganic instances so far. Herein, we report four new 3D SCN−-bridged molecular double perovskites with a general formula of A2[CdM′(SCN)6] (A/M′ = K+/Ni2+, Me2NH2+/Ni2+, Me2NH2+/Mn2+, Me3S+/Cd2+), including three unprecedented hybrid instances incorporating organic cations. A detailed comparison between these SCN−-bridged molecular perovskites and some azido-bridged analogues, on their host–guest interactions and structural distortions, revealed that the bent Cd–S–C angles in these SCN−-bridged molecular perovskites vary in a narrow range, endowing their frameworks with a high structural distortion and a relatively strong structural rigidity. The present study not only extends SCN−-bridged 3D molecular perovskites to enrich the perovskite family, but also paves a way for the rational design of new molecular perovskites. [ABSTRACT FROM AUTHOR]

An unexpected dominance of the coordination affinity of the sulfate anion over those of two organic chelating ligands, (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm) and pyridin-2-ylmethanamine (pma), was observed during the study of the solvothermal assembly of [Co11(mbm)6(pma)2(SO4)8(H2O)6(CH3OH)6]·5CH3OH (1), from CoSO4·7H2O at 100 °C in methanol. ESI-MS of solutions at different periods of the assembly reveal a hierarchical sequence, [Co1] → [Co2] → [Co3] → [Co4] → [Co5] → [Co9], where the lower nuclearity species are richer in Co2+ and SO42− before the inclusion of more mbm ligands at the last step. Its crystal structure consists of an almost symmetrical wheel of nine cobalt atoms, [Co9(mbm)6(SO4)8(H2O)6] in edge-sharing octahedral coordination arranged in triangles with two peripheral dangling [Co(pma)(CH3OH)3]. The sulfate ions exhibit three different coordination modes, two in μ6-, two in μ3- and four as μ2-bridging. Its thermal, optical and magnetic properties are also reported. [ABSTRACT FROM AUTHOR]

A new series of luminescent phosphine copper(I) complexes with cyano- and hydroxyl-substituted 2,2′-bipyridine ligands [CuI(bpy(CN)2)(P(PhX)3)2](ClO4) [X = H (1); Me (2); Cl (3)], [CuI(bpy(CN)2)(POP)](ClO4) (4), [CuI(bpy(OH)2)(PPh3)2](ClO4) (5) and [CuI(bpy(OH)2)(POP)](ClO4) (6) have been synthesized and characterized. Three of these complexes have been structurally characterized by using X-ray crystallography. The effect of the attaching –CN and –OH groups at the ortho-positions of bpy ligand was investigated. In CH2Cl2 solution, these complexes show yellow to orange phosphorescence, with the emission maxima not only sensitive to the electronic nature of the bipyridine ligands, but also considerably varied with the modification of phosphine ligands. In addition, these complexes show intense tunable green to yellow emissions in their solid state. To elucidate the electronic structures and transitions of these complexes, density functional theory (DFT) calculations on representative examples revealed that the lowest energy electronic transition associated with these complexes predominantly originates from metal-to-ligand charge transfer transitions (MLCT). [ABSTRACT FROM AUTHOR]

A regio- and stereoselective iodolactonization of internal electron-deficient olefinic acids has been reported, which provides a straightforward access to a series of multi-functionalized seven-membered lactones containing two consecutive chiral centers. The ester substituents on the olefins played a key role in achieving high regioselectivity. This result was proved through experiments and DFT calculations. [ABSTRACT FROM AUTHOR]

We prepared five diarylethenes containing 2-aryl-imidazole as the ethene bridge (L1–L5), and introduced response sites in imidazole rather than in the traditional appended aryl units to regulate their photochromism and thermal stability under acid stimulus. The results show that we can change the thermal stability from P- to T-type, and prevent their photoactivity by acidification, and it is clarified that the stronger the acid or the more acid added, the faster the decay rate of the diarylethene photostability. Furthermore, the prohibited photoactivity could be restored by neutralization with an equimolar amount of base. [ABSTRACT FROM AUTHOR]

Analyses of the structural information of molecular fragments from the mass spectra of the solid-state products and their reaction solutions allow for the understanding of their formation and of their diverse properties. The reaction of CuCl2 and (1-methyl-1H-benzo[d]imidazole-2-yl)methanol (HL) led only to crystals containing molecular dimers of [Cu2(L)2Cl2] (Cu2). The CuII–CuII distance and Cu–OR–Cu angle in the structure are 3.044 Å and 104.8°, respectively. The magnetic susceptibility (3–400 K) is characterized by a very strong intradimer antiferromagnetic interaction of J = −465 and interdimer zj = −0.83 cm−1. But mass spectrometry of a dissolved single crystal in different source energies identifies both its fragmentation and oligomerization to [Cu II3 ] and [Cu II4 ]. DFT calculations give the relative stabilization energies of the fragments observed in ESI-MS to provide a formation process. [ABSTRACT FROM AUTHOR]

Pd(ii)-Catalyzed direct C(sp3)–H germylation of α-AA derivatives with the assistance of a bidentate auxiliary for the efficient synthesis of β-germyl-α-amino amides is reported. This protocol features good generality for primary and secondary C–H bonds of aliphatic amides. Mechanistic studies show that a crucial five-membered palladacycle intermediate may play a key role in this process. [ABSTRACT FROM AUTHOR]

The conjugation of bridging bis(diphenylphosphine oxide) alkane or arene ligands was found to control the structural dimensionality and the emission color of complexes from reactions with SmIII(hfac)3(H2O)2 (hfac− = hexafluoroacetylacetonato) while retaining the Sm…Sm distances. Bis(diphenylphosphine oxide)-1,4-butane (L1) affords a one-dimensional (1D) ribbon {Sm(hfac)3(L1)}∞ (1) that emits red color, while bis(diphenyl-phosphinoyl)-1,4-benzene (L2) results in a two-dimensional (2D) network {Sm(hfac)2(CF3COO)(L2)3}∞ (2) and near-white emission, but bis(diphenyl-phosphinoyl)-9,10-anthracene (L3) forms a zero-dimensional (0D) cyclic structure {Sm(hfac)3(L3)}2 (3) with strong π…π interactions that emit green color. Noticeably, the conjugation change is accompanied by a configurational change of coordination from trans for 1 and 2 to cis for 3. The color change is associated with the superposition of ligand and Sm based electronic band energies and their intensities. Such white light emission by a single compound having contributions from different building components is quite rare. [ABSTRACT FROM AUTHOR]

We showed that the simple organic salt bromocholine bromide is a molecular ferroelectric with a moderate ferroelectric phase transition temperature (329 K). The order–disorder dynamic transition of organic cations results in symmetry breaking from the centrosymmetric paraelectric phase (P21/m) to polar ferroelectric phase (P21), affording a moderate spontaneous polarization of 1.0 μC cm−2 for the ferroelectric phase, as well as a switchable SHG signal and pyroelectric property with feasible “on/off” contrasts. [ABSTRACT FROM AUTHOR]

The newly synthesized ionic triple salt Ru–Er, {[RuII(bpy)2(dbim)][ErIII(hfac)4][CF3COO]·H2O} (bpy = 2,2′-bipyridine; hfac− = hexafluoroacetylacetonate; dbim = 2,2′-dibenzimidazole) exhibits near-infrared (NIR) emission at 1535 nm by intermolecular Ru → Er (d → f) energy transfer across supramolecular interactions when pumped within the Ru(ii) 3MLCT band. It is the first such observation for a transition metal–lanthanide ionic pair. [ABSTRACT FROM AUTHOR]

Herein, quasi-square planar CuII(Hmbm)Cl2 (CBC, Hmbm = (1-methyl-1H-benzo[d]imidazol-2-yl)methanol) was arranged in a pseudo orthogonal way to form Cl-bridged chains, and further π…π interactions resulted in distorted hexagonal layers. DFT calculations reveal a bond strength order of Cu–Cl ＞ Cu–O/N > Cu…Cl. ESI-MS data reveal several small fragments from CBC, but oligomeric [CuII2], [CuII3], and [CuII4] for non-zero in-source energies; MS data indicates the occurrence of several chemical processes, viz. splitting of the ligand, oligomerization, and redox reaction of alcohol to aldehyde and CuII to CuI. Gibbs free energies for the fragments were estimated using DFT. The magnetic susceptibility was modeled with the ferromagnetic coupling J(Cu–Cl2a…Cu) = +0.99(30) cm−1 and J′(π…π) = +0.35(16) cm−1 and g = 2.38(2). HF-EPR determined the anisotropic g-values, gx = 2.24, gy = 2.16, and gz = 2.09, and a hyperfine constant of Az = 450 G. DFT calculations from crystal structure data reveal a J(Cu–Cl2a…Cu) of +3.6 at 296 K and +4.1 cm−1 at 90 K that dominates the magnetic properties, whereas J′(π…π) = 0.04 cm−1 is negligibly small. [ABSTRACT FROM AUTHOR]

A new molecular crystal with supramolecular layers assembled by a Mn(iii)–Schiff-base dimer and fumaric acid was investigated by means of variable-temperature single-crystal structural analyses. The Mn(iii)–Schiff-base dimer reveals remarkable thermally-induced deformation and hence causes anomalously large positive and negative anisotropic thermal expansions in the supramolecular layers, providing a new type of promising weak supramolecular synthon for designing sensitive thermomechanical actuators. [ABSTRACT FROM AUTHOR]

A novel two-dimensional Heisenberg ferromagnet with a flexible organic layer, [C6H5(CH2)4NH3]2[CuCl4], undergoes ferroelastic, ferroelectric and ferromagnetic transitions at 337, 143 and 7.8 K, respectively. The ferromagnet was characterized by variable-temperature thermal measurements, in situ single-crystal X-ray structure analyses, anisotropic dielectric measurements, and pyroelectric and magnetic analyses. Differing from the other layered perovskite-like compounds, this compound revealed an extraordinary distorted polar structure with five times the cell volume at its polar phase because of the flexibility of the organic layer. Hence, this presents an approach to introduce spontaneous electric polarization into the Heisenberg ferromagnet for single-phase multiferroics. Moreover, due to the cooperation between the frozen [C6H5(CH2)4NH3]+ cations and the tilting of the CuCl6 octahedra, this potential multiferroic compound simultaneously exhibits dielectric and magnetic bistabilities during both the ferroelastic and ferroelectric transitions. [ABSTRACT FROM AUTHOR]

The research on metal–organic frameworks (MOFs) has been developing at an extraordinary pace in its two decades of existence, as judged by the exponential growth of novel structures and the constant expansion of its applicability and research scope. A major part of the research and its success are due to the vital role of the concept of mixed organic ligands in the design, tuning and functions. This perspective, therefore, reviews the recent advances in MOFs based on this concept, which is generally based on employing a small polydentate ligand (here labelled as “nodal ligand”) to form either clusters, rods or layers, which are then connected by a second ditopic linker ligand to form the framework. The structures of the materials can be grouped into the following three categories: layer-spacer (usually known as pillared-layer), rod-spacer, and cluster-spacer based MOFs. Depending on the size and geometry of the spacer ligands, interpenetrations of frameworks are occasionally found. These MOFs show a wide range of properties such as (a) crystal-to-crystal transformations upon solvent modifications, post-synthetic metal exchange or ligand reactions, (b) gas sorption, solvent selectivity and purification, (c) specific catalysis, (d) optical properties including colour change, luminescence, non-linear optic, (e) short- and long range magnetic ordering, metamagnetism and reversible ground-state modifications and (f) drug and iodine carriers with controlled release. In the following, we will highlight the importance of the above concept in the design, tuning, and functions of a selection of existing MOFs having mixed organic ligands and their associated structures and properties. The results obtained so far using this concept look very promising for fine-tuning the pore size and shape for selective adsorption and specificity in catalytic reactions, which appears to be one way to propel the advances in the application and commercialization of MOFs. [ABSTRACT FROM AUTHOR]

Three new polynuclear complexes, [Co7(bm)12]·(ClO4)2·13H2O (1), [Co4(bm)4Cl4(C3H7OH)4] (2), and [Co4(bm)4(μ-HCO2)2(μ2-HCO2)2(C3H7OH)2] (3) (Hbm = (1H-Benzimidazol)-methanol), have been synthesized and characterized by elemental analysis, IR, powder X-ray diffraction and X-ray single-crystal diffraction. Compound 1features a centrosymmetric wheel-like heptanuclear Co(ii) cluster. Compound 2having a I41/aspace group exhibits a tetranuclear Co(ii) cluster with a cubane topology in which the central Co(ii) ion and oxygen atoms from bm occupy the alternate vertices of the cube. However, compound 3has a tetranuclear Co(ii) cluster with a C2/cspace group different from that of compound 2. These results show that the geometries and sizes of the corresponding anions as well as their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Magnetic properties of 1–3in the 2–300 K have also been discussed. The {Co7} (1) and {Co4} (2) cores display dominant ferromagnetic interactions while the {Co4} (3) core displays dominant anti-ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

The solvothermal reaction of In(iii) and 1,2,4,5-benzeneteracarboxylic acid with the presence of piperazine leads to the generation of a novel 3D chiral porous coordination polymer with PtS topological net. Interestingly, the resulting crystals were not a racemic mixture but enantiomeric excess, which was confirmed by the measurement of optical rotation of bulk samples using solid vibrational circular dichroism (VCD) spectra and the solid circular dichroism (CD) spectra based on large crystals from one crystallization. High-pressure CO2and CH4adsorption measurement at 298 K reveals that activated 1can absorb 45.8 cm3(STP)/g CO2at 22 atm and 22.5 cm3(STP)/g CH4at 25 atm. [ABSTRACT FROM AUTHOR]

Hydrothermal reaction of Co(ClO4)2·6H2O with 2-ethoxy-6-(iminomethyl)phenol (Heimp) or 3-ethoxysalicylaldoxime (H2eosa) leads to the formation of two completely different CoIIcomplexes [Co7(eimp)6(OMe)6]·2ClO4(1) and [Co13(eosao)8(Heosao)6(ClO4)4]·H2O (2). Compound 1is a disc-like heptanuclear CoIIcluster with all the eimp−ligands displaying the η1: η2: η1: μ2binding mode. Compound 2is a butterfly-like nano-tridecanuclear CoIIcluster and the oximation of iminomethyl group results in its complicated binding modes. Four of the six Heosao−ligands adopt the η1: η2: η1: μ2mode and the other two take the η1: η2: η1: η1: μ3fashion, while eight eosao2−ligands are in the η2: η1: η2: μ4, η1: η3: η1: η2: μ5manner. Microwave heating during the synthetic process will dramatically improve the reaction rate and yield of 1, which however, is not valid for the formation of 2. Electrospray ionization mass spectrometry (ESI-MS) solution analysis was performed, which reveals a ligand substitution reaction of the core bridge for 1. For 2, the result of ESI-MS indicates that the Co13cluster still exists in solution, and maintains a conformation similar to that observed in the crystal structure. Magnetic studies show that 1exhibits a dominated ferromagnetic coupling between the CoIIions below 30 K, while 2is a typical antiferromagnetic system. [ABSTRACT FROM AUTHOR]

Developing new and understanding multicomponent reactions (MCRs) is an appealing but challenging task. Herein, Rh(iii)-catalyzed multicomponent double C-H annulations of cyclic diimines (or diketones and acetone), alkynes, and ammonium acetate to assemble functionalized 1,1'-biisoquinolines and C-bridged 1,1'-bisisoquinolines with controllable 14 N/ 15 N editing in one shot has been developed. Through a combination of isotopic-labeling ( 2 H, 18 O, and 15 N) experiments, crystallography, and time-dependent ESI-MS, the reaction process was studied in detail. Ammonium acetate accounts for two rounds of Hofmann elimination and iminization, thus leading to an unprecedented imine dance, cyclic imine → N -alkenyl imine → NH imine. The N -alkenyl imine can immediately guide a C-H annulation (N-retention channel), and some of it is converted into NH-imine to trigger another annulation (N-exchange channel). The channels and 15 N ratios can be regulated by the reaction mode and acidity. Moreover, the resulting 1,1'-biisoquinolines are a privileged ligand scaffold which is exemplified herein by a hydrazine-iodine exchange reaction to form drug-like benzo[ c ]cinnolines., Competing Interests: The authors declare no competing financial interest., (This journal is © The Royal Society of Chemistry.)

We report a phosphine-directed ruthenium-catalyzed C8-selective alkylation of naphthalenes with alkenes. This protocol provides straightforward access to a large library of electron-rich C8-alkyl substituent 1-naphthphosphines, which outperformed common commercial phosphines and their precursors in the Pd-catalyzed Suzuki-Miyaura coupling of aryl bromides with alkylboronic acid.

An unexpected dominance of the coordination affinity of the sulfate anion over those of two organic chelating ligands, (1-methyl-1H-benzo[d]imidazol-2-yl)methanol (Hmbm) and pyridin-2-ylmethanamine (pma), was observed during the study of the solvothermal assembly of [Co11(mbm)6(pma)2(SO4)8(H2O)6(CH3OH)6]·5CH3OH (1), from CoSO4·7H2O at 100 °C in methanol. ESI-MS of solutions at different periods of the assembly reveal a hierarchical sequence, [Co1] → [Co2] → [Co3] → [Co4] → [Co5] → [Co9], where the lower nuclearity species are richer in Co2+ and SO42- before the inclusion of more mbm ligands at the last step. Its crystal structure consists of an almost symmetrical wheel of nine cobalt atoms, [Co9(mbm)6(SO4)8(H2O)6] in edge-sharing octahedral coordination arranged in triangles with two peripheral dangling [Co(pma)(CH3OH)3]. The sulfate ions exhibit three different coordination modes, two in μ6-, two in μ3- and four as μ2-bridging. Its thermal, optical and magnetic properties are also reported.

Analyses of the structural information of molecular fragments from the mass spectra of the solid-state products and their reaction solutions allow for the understanding of their formation and of their diverse properties. The reaction of CuCl 2 and (1-methyl-1H-benzo[d]imidazole-2-yl)methanol (HL) led only to crystals containing molecular dimers of [Cu 2 (L) 2 Cl 2 ] (Cu2). The Cu II -Cu II distance and Cu-OR-Cu angle in the structure are 3.044 Å and 104.8°, respectively. The magnetic susceptibility (3-400 K) is characterized by a very strong intradimer antiferromagnetic interaction of J = -465 and interdimer zj = -0.83 cm -1 . But mass spectrometry of a dissolved single crystal in different source energies identifies both its fragmentation and oligomerization to [Cu] and [Cu]. DFT calculations give the relative stabilization energies of the fragments observed in ESI-MS to provide a formation process.

Efficient oxygen evolution reaction catalysts can be prepared via controlled pyrolysis of molecular platforms, and there is still minimal mechanistic understanding of such pyrolysis processes. Here, we introduce a 3-MeOsalophen-ligated cobalt complex as a precursor to obtain a Co-based OER electrocatalyst via controlled pyrolysis under an inert atmosphere. In our case, the unique N, O chelation mode of the 3-MeOsalophen ligand (bis[3-methoxysalicylydene]-1,2 iminophenylenediamine) was used to synthesis a Co 2 complex [Co 2 (3-MeOsalophen)(Cl) 3 (CH 3 OH) 2 ]. By regulating the pyrolysis conditions, we successfully obtained a N-doped carbon Co/CoO x core-shell nanostructure. More importantly, TG-MS was first adopted for tracking the decomposition products of the complex in the pyrolysis process, further finding out the evolution mechanism from Co 2 to the core-shell nanostructure. As an electrocatalyst for the oxygen evolution reaction, the core-shell Co/CoO x @NC-800 nanostructure achieves an ultralow overpotential of 288 mV at 10 mA cm -2 in 1 M KOH solution. This work offers guiding insight into controlled pyrolysis via TG-MS analysis, using a novel complex precursor for precise regulation of heteroatom-doped (3d) transition metal-based electrocatalysts.

Pd(ii)-Catalyzed direct C(sp3)-H germylation of α-AA derivatives with the assistance of a bidentate auxiliary for the efficient synthesis of β-germyl-α-amino amides is reported. This protocol features good generality for primary and secondary C-H bonds of aliphatic amides. Mechanistic studies show that a crucial five-membered palladacycle intermediate may play a key role in this process.

The conjugation of bridging bis(diphenylphosphine oxide) alkane or arene ligands was found to control the structural dimensionality and the emission color of complexes from reactions with SmIII(hfac)3(H2O)2 (hfac- = hexafluoroacetylacetonato) while retaining the SmSm distances. Bis(diphenylphosphine oxide)-1,4-butane (L1) affords a one-dimensional (1D) ribbon {Sm(hfac)3(L1)}∞ (1) that emits red color, while bis(diphenyl-phosphinoyl)-1,4-benzene (L2) results in a two-dimensional (2D) network {Sm(hfac)2(CF3COO)(L2)3}∞ (2) and near-white emission, but bis(diphenyl-phosphinoyl)-9,10-anthracene (L3) forms a zero-dimensional (0D) cyclic structure {Sm(hfac)3(L3)}2 (3) with strong ππ interactions that emit green color. Noticeably, the conjugation change is accompanied by a configurational change of coordination from trans for 1 and 2 to cis for 3. The color change is associated with the superposition of ligand and Sm based electronic band energies and their intensities. Such white light emission by a single compound having contributions from different building components is quite rare.

The newly synthesized ionic triple salt Ru-Er, {[Ru II (bpy) 2 (dbim)][Er III (hfac) 4 ][CF 3 COO]·H 2 O} (bpy = 2,2'-bipyridine; hfac - = hexafluoroacetylacetonate; dbim = 2,2'-dibenzimidazole) exhibits near-infrared (NIR) emission at 1535 nm by intermolecular Ru → Er (d → f) energy transfer across supramolecular interactions when pumped within the Ru(ii) 3 MLCT band. It is the first such observation for a transition metal-lanthanide ionic pair.

Herein, quasi-square planar Cu II (Hmbm)Cl 2 (CBC, Hmbm = (1-methyl-1H-benzo[d]imidazol-2-yl)methanol) was arranged in a pseudo orthogonal way to form Cl-bridged chains, and further ππ interactions resulted in distorted hexagonal layers. DFT calculations reveal a bond strength order of Cu-Cl > Cu-O/N ≫ CuCl. ESI-MS data reveal several small fragments from CBC, but oligomeric [Cu], [Cu], and [Cu] for non-zero in-source energies; MS data indicates the occurrence of several chemical processes, viz. splitting of the ligand, oligomerization, and redox reaction of alcohol to aldehyde and Cu II to Cu I . Gibbs free energies for the fragments were estimated using DFT. The magnetic susceptibility was modeled with the ferromagnetic coupling J(Cu-Cl2aCu) = +0.99(30) cm -1 and J'(ππ) = +0.35(16) cm -1 and g = 2.38(2). HF-EPR determined the anisotropic g-values, g x = 2.24, g y = 2.16, and g z = 2.09, and a hyperfine constant of A z = 450 G. DFT calculations from crystal structure data reveal a J(Cu-Cl2aCu) of +3.6 at 296 K and +4.1 cm -1 at 90 K that dominates the magnetic properties, whereas J'(ππ) = 0.04 cm -1 is negligibly small.

The research on metal-organic frameworks (MOFs) has been developing at an extraordinary pace in its two decades of existence, as judged by the exponential growth of novel structures and the constant expansion of its applicability and research scope. A major part of the research and its success are due to the vital role of the concept of mixed organic ligands in the design, tuning and functions. This perspective, therefore, reviews the recent advances in MOFs based on this concept, which is generally based on employing a small polydentate ligand (here labelled as "nodal ligand") to form either clusters, rods or layers, which are then connected by a second ditopic linker ligand to form the framework. The structures of the materials can be grouped into the following three categories: layer-spacer (usually known as pillared-layer), rod-spacer, and cluster-spacer based MOFs. Depending on the size and geometry of the spacer ligands, interpenetrations of frameworks are occasionally found. These MOFs show a wide range of properties such as (a) crystal-to-crystal transformations upon solvent modifications, post-synthetic metal exchange or ligand reactions, (b) gas sorption, solvent selectivity and purification, (c) specific catalysis, (d) optical properties including colour change, luminescence, non-linear optic, (e) short- and long range magnetic ordering, metamagnetism and reversible ground-state modifications and (f) drug and iodine carriers with controlled release. In the following, we will highlight the importance of the above concept in the design, tuning, and functions of a selection of existing MOFs having mixed organic ligands and their associated structures and properties. The results obtained so far using this concept look very promising for fine-tuning the pore size and shape for selective adsorption and specificity in catalytic reactions, which appears to be one way to propel the advances in the application and commercialization of MOFs.

We report a study of the comparative solvothermal syntheses, using traditional and microwave ovens, of two complexes [Co4(μ3-OMe)4(L)4(MeOH)4], where (HL = Hhmb, 2-hydroxy-3-methoxy-benzaldehyde (1) or Hheb = 2-hydroxy-3-ethoxy-benzaldehyde (2)), their crystal structures and magnetic properties in the solid state and the ESI-MS of the solutions. The microwave heating is more efficient in time and quality of crystals than the traditional one where what is achieved per minute by the former takes an hour by the latter. The structures consist of stacks of high-symmetry [Co4(μ3-OMe)4] cubanes in tetragonal space groups. The inner cores of the clusters have almost the same geometry but the distances between them are longer for the ethoxy than the methoxy derivative. The magnetic interaction within the cluster is ferromagnetic in both cases but spin-orbit competes with it. The different isothermal magnetizations at low temperatures may be due to different intercluster coupling. Electrospray ionization mass spectrometry (ESI-MS) from methanol solution reveals an exchange of methoxide for hydroxide and in ethanol of methoxide for ethoxide at different proportions suggesting a probable "step by step" substitution. Interestingly, besides the [Co4] cubane a number of higher nuclearity species [Co5] and [Co7] were also observed but are not expected under electrospray conditions. This can easily happen by the re-assembly of the smaller fragments produced by ionization process. This unique feature opens up new possibilities for the systematic screening of reactions in search for new cluster architectures, which may then be realised in the solid state.

Two new 3D coordination polymers based on tetranuclear clusters, {[Co(4)(ina)(5)(μ(3)-OH)(2)(H(2)O)(EtOH)]-NO(3)·2EtOH·4H(2)O}(n) (1) (Hina = isonicotinic acid) and {[Ni(4)(ina)(5)(μ(3)-OH)(2)(EtCOO)]·6EtOH·2H(2)O}(n) (2), were obtained by the solvothermal reactions from Hina and different metal salts. The [M(4)(μ(3)-OH)(2)] cores act as 7- and 9-connected nodes and are extended through ina linkers to highly-connected frameworks with vmr net for 1 and bct-9-P2(1)/c net for 2. Both the desolvated frameworks display effective gas sorption capacities of N(2) and H(2) with Langmuir surface areas of 546 and 917 m(2) g(-1) for 1 and 2, respectively. Magnetic studies show spin canting and spin-glass behaviours with T(g) = 6.0 and 15.0 K for 1 and 2, respectively. The intra- and inter-tetramer coupling interactions and cooperative magnetic correlation greatly influence the bulk magnetic behaviours in this system.

Three new polynuclear complexes, [Co(7)(bm)(12)]·(ClO(4))(2)·13H(2)O (1), [Co(4)(bm)(4)Cl(4)(C(3)H(7)OH)(4)] (2), and [Co(4)(bm)(4)(μ-HCO(2))(2)(μ(2)-HCO(2))(2)(C(3)H(7)OH)(2)] (3) (Hbm = (1H-Benzimidazol)-methanol), have been synthesized and characterized by elemental analysis, IR, powder X-ray diffraction and X-ray single-crystal diffraction. Compound 1 features a centrosymmetric wheel-like heptanuclear Co(II) cluster. Compound 2 having a I4(1)/a space group exhibits a tetranuclear Co(II) cluster with a cubane topology in which the central Co(II) ion and oxygen atoms from bm occupy the alternate vertices of the cube. However, compound 3 has a tetranuclear Co(II) cluster with a C2/c space group different from that of compound 2. These results show that the geometries and sizes of the corresponding anions as well as their coordinating and hydrogen-bonding properties are essential in determining the final structures of the assemblies. Magnetic properties of 1-3 in the 2-300 K have also been discussed. The {Co(7)} (1) and {Co(4)} (2) cores display dominant ferromagnetic interactions while the {Co(4)} (3) core displays dominant anti-ferromagnetic interactions., (This journal is © The Royal Society of Chemistry 2011)

The solvothermal reaction of In(III) and 1,2,4,5-benzeneteracarboxylic acid with the presence of piperazine leads to the generation of a novel 3D chiral porous coordination polymer with PtS topological net. Interestingly, the resulting crystals were not a racemic mixture but enantiomeric excess, which was confirmed by the measurement of optical rotation of bulk samples using solid vibrational circular dichroism (VCD) spectra and the solid circular dichroism (CD) spectra based on large crystals from one crystallization. High-pressure CO(2) and CH(4) adsorption measurement at 298 K reveals that activated 1 can absorb 45.8 cm(3) (STP)/g CO(2) at 22 atm and 22.5 cm(3) (STP)/g CH(4) at 25 atm., (This journal is © The Royal Society of Chemistry 2011)

A new 2D coordination polymer Co3(OH)2(pa)2(ina)2 (1, pa = 3-(1H-benzimidazol-2-yl) propanoic carboxylate, ina = isonicotinate) contained uncommon, linear Co(ii) trimers of mixed Td-Oh-Td geometries, exhibits spin canting below 20 K. Such magnetic behavior mainly arises from the Dzyaloshinski-Moriya interaction from the anisotropic, mixed geometries trimeric Co(II) ions to the crimpled 2D network based on the nature of the binding modes of Co(II)-carboxylate trimer and the effect of the intertrimers arrangement of 1. The mixed single-carboxylate-aromatic amine ligands bridged metal systems display a new structurally authenticated example of a thick 2D layer, and also indicate homometallic Co(II) clusters with Td-Oh-Td mixed-geometries can result in relatively obvious noncompensation moments, according to different efficient spins of Co(II) at very low temperature, in spite of antiferromagnetic intracluster interactions.

A microporous 3D cobalt(II) coordination polymer featuring pillared layers [Co(2)(ma)(ina)](n) x 2nH(2)O (1 x 2H(2)O) (ma = malate, ina = isonicotinate) was generated by hydrothermal treatment with a void volume of 25.8%, in which the in-situ generated ma ligands connect the Co(II) ions into a 2D lattice with mixed and multiple exchange-bridges, affording a new geometrical topology different from the Kagomé lattice and leading to spin frustration. The rigid ina-pillared metallic-layered structure could retain 3D structural ordering upon guest removal and exchange. By soaking guest-free host in MeOH and methanamide (HCONH(2)) solutions, single crystals of dehydrated were transformed into single crystals of 1 x MeOH and 1 x HCONH(2), respectively, without apparent host-structural changes. 1 can also be rehydrated into 1 x 2H(2)O'. The guest-inclusion crystals have been characterized by X-ray single-crystal diffraction at 293 K and 93 K, confirming the single-crystal-to-single-crystal transformations and providing detailed information of the guest molecules confined in the subnanospace and host-guest and/or guest-guest hydrogen-bonding interactions. The magnetic behaviours of this family of porous magnetic materials are complex due to the influences of multiple metal sites, intra- and inter-layer exchanges, spin-orbit coupling, as well as geometrical frustration, which show magnetic ordering at <2 K, 3.5 K, 3.5 K, and 8 K for 1, 1 x MeOH, 1 x HCONH(2), and 1 x 2H(2)O, respectively, due to the different size of guest molecules along with the different host-guest interaction, which may slightly modify the path of magnetic exchange, decrease the intensity of the spin-frustration in the 2D lattice, and cooperatively enhance the magnetic ordering temperature.

Single crystals of a neutral, microporous, laminated metal-organic framework (MOF)[Fe(pydc)(4,4'-bipy)]xH(2)O (1xH(2)O)(H(2)pydc = 2,5-dicarboxypyridine, 4,4'-bipy = 4,4'-bipyridine) were generated by hydrothermal synthesis, and its crystal structure was determined. 1xH(2)O retains the framework robustness to ca. 370 degrees C and is insoluble in common organic solvents. By soaking in MeOH and EtOH solutions, 1xH(2)O was transformed directly from the parent single crystals into single crystals of 1xMeOH or 1xEtOH, respectively. Meanwhile, 1xH(2)O shrank to the guest-free framework (h) or (v), respectively, under appropriate heating (up to 160 degrees C in N(2)) or vacuum treatment (10 mmHg) at room temperature. Compared to that of 1xH(2)O, the unit-cell volume of 1xEtOH slightly increases by 2.9%, whereas those of (h) or (v) are reduced by 8.2 and 6.6%, respectively. The anhydrous (v) was found to be highly chemically reactive, taking up ethanol vapor to furnish the solvated crystal structure of an 'expanded' framework 1xEtOH. In a mixture of ethanol-DMF or ethanol-benzene, a selective exchange process was observed, with only ethanol molecules exchanged into the structure due to the limited free size of the channels in the framework of. All the transformed crystals have also been characterized by X-ray single-crystal diffraction to understand the crystal-to-crystal transformation, which have different free volumes (6.5-20.4%).