Magneto-Structural Correlation of Five-Coordinate Trigonal Bipyramidal High Spin Cobalt(II) Complexes.

Here, we combined magnetometry, multi-frequency electronic paramagnetic resonance, and wave function based ab initio calculations to investigate magnetic properties of two high spin Co(II) complexes Co(BDPRP) (BDPRP=2,6-bis((2-(S)-di(4-R)phenylhydroxylmethyl-1-pyrrolidi-nyl)methyl)pyridine, R=H for 8; R=tBu for 9). Complexes 8 and 9 featuring effective D3h symmetry were found to possess D=24.0 and 32.0 cm-1, respectively, in their S=3/2 ground states of 1 e ' ' d x z / y z 4 1 e ' d x y / x 2 - y 2 2 1 a 1 ' d z 2 1 ${{\left(1{{\rm e}}^{{\rm { {^\prime}}}{\rm { {^\prime}}}}\right({d}_{xz/yz}\left)\right)}^{4}{\left(1{{\rm e}}^{{\rm { {^\prime}}}}\right({d}_{{xy/{x}^{2}-y}^{2}}\left)\right)}^{2}{\left(1{{\rm a}}_{1}^{{\rm { {^\prime}}}}\right({d}_{{z}^{2}}\left)\right)}^{1}}$ . Ligand field analyses revealed that the low-lying d-d excited states make either positive or vanishing contributions to D. Hence, total positive D values were measured for 8 and 9, as well as related D3h high spin Co(II) complexes. In contrast, negative D values are usually observed for C3v congeners. In-depth analyses suggested that lowering symmetry from D3h to C3v induces orbital mixing between 1 e d x z / y z ${1{\rm e}\left({d}_{xz/yz}\right)}$ and 2 e d x y / x 2 - y 2 ${2{\rm e}\left({d}_{{xy/{x}^{2}-y}^{2}}\right)}$ and admixes excited state 4 A 2 1 e → 2 e ${{}^{4}{{\rm A}}_{2}\left(1e\to 2e\right)}$ into the ground state. Both factors turn the total D value progressively negative with the increasing distance (δ) of the Co(II) center out of the equatorial plane. Therefore, δ determines the sign and magnitude of final D values of five-coordinate trigonal bipyramidal S=3/2 Co(II) complexes as measured for a series of such species with varying δ.

Field-Induced Slow Magnetic Relaxation in Mononuclear Cobalt(II) Complexes Decorated by Macrocyclic Pentaaza Ligands.

Two cobalt(II) complexes [CoL1](OTf)2 (1, L1 = 6,6''-di(anilino)-4'-phenyl-2,2':6',2''-terpyridine) and [CoL2](OTf)2·MeOH (2, L2 = 6,6''-di(N,N-dimethylamino)-4'-phenyl-2,2':6',2''-terpyridine) were synthesized and characterized. Crystal structure analyses showed that the spin carries were coordinated by five N atoms from the neutral pentaaza ligands, forming distorted trigonal bipyramidal coordination environments. Ab initio calculations revealed large easy-axial anisotropy in complexes 1 and 2. Magnetic measurements suggest that complexes 1 and 2 are field-induced single-molecule magnets, whose relaxations are mainly predominated by Raman and direct processes.

Near-Infrared Emissive Hypervalent Compounds with Germanium(IV)-Fused Azobenzene π-Conjugated Systems.

A novel molecular design for showing near-infrared (NIR) emission is still required for satisfying growing demands for NIR-light technology. In this research, hypervalent compounds with germanium (Ge)-fused azobenzene (GAz) scaffolds were discovered that can exhibit NIR emission (λPL =690∼721 nm, ΦPL =0.03∼0.04) despite compact π-conjugated systems. The unique optical properties are derived from the trigonal bipyramidal geometry of the hypervalent compounds constructed by combination of Ge and azobenzene-based tridentate ligands. Experimental and theoretical calculation results disclosed that the germanium-nitrogen (Ge-N) coordination at the equatorial position strongly reduces the energy level of the LUMO (lowest unoccupied molecular orbital), and the three-center four-electron (3 c-4 e) bond in the apical position effectively rises the energy level of the HOMO (highest occupied molecular orbital). It is emphasized that large narrowing of the HOMO-LUMO energy gap is achieved just by forming the hypervalent bond. In addition, the narrow-energy-gap property can be enhanced by extension of π-conjugation. The obtained π-conjugated polymer shows efficient NIR emission both in solution (λPL =770 nm and ΦPL =0.10) and film (λPL =807 nm and ΦPL =0.04). These results suggest that collaboration of a hypervalent bond and a π-conjugated system is a novel and effective strategy for tuning electronic properties even in the NIR region.

Water-Based Synthesis of Palladium Trigonal Bipyramidal/Tetrahedral Nanocrystals with Enhanced Electrocatalytic Oxidation Activity.

Well-defined palladium trigonal bipyramidal/tetrahedral nanocrystals were synthesized by an aqueous-phase hydrothermal method. The final products were a mixture of trigonal bipyramidal and tetrahedral nanocrystals. Statistics indicated that there were more trigonal bipyramids than tetrahedra in the products. Ethylenediamine tetraacetic acid disodium salt (EDTA-2Na) was proven to be essential in controlling the final shapes of palladium nanocrystals. Some control experiments were also conducted to investigate the shape evolution and formation mechanisms. The synthesized palladium nanocrystals showed enhanced catalytic properties for ethanol and glycerol electrooxidation in alkaline medium. This work provides a new method in preparing Pd nanomaterials with well-defined shapes.

Quantitative Estimation of Ising-Type Magnetic Anisotropy in a Family of C3 -Symmetric CoII Complexes.

In this paper, the influence of the structural and chemical effects on the Ising-type magnetic anisotropy of pentacoordinate CoII complexes has been investigated by using a combined experimental and theoretical approach. For this, a deliberate design and synthesis of four pentacoordinate CoII complexes [Co(tpa)Cl]⋅ClO4 (1), [Co(tpa)Br]⋅ClO4 (2), [Co(tbta)Cl]⋅(ClO4 )⋅(MeCN)2 ⋅(H2 O) (3) and [Co(tbta)Br]⋅ClO4 (4) by using the tripodal ligands tris(2-methylpyridyl)amine (tpa) and tris[(1-benzyl-1 H-1,2,3-triazole-4-yl)methyl]amine) (tbta) have been carried out. Detailed dc and ac measurements show the existence of field-induced slow magnetic relaxation behavior of CoII centers with Ising-type magnetic anisotropy. A quantitative estimation of the zero-field splitting (ZFS) parameters has been effectively achieved by using detailed ab initio theory calculations. Computational studies reveal that the wavefunction of all the studied complexes has a very strong multiconfigurational character that stabilizes the largest ms =±3/2 components of the quartet state and hence produce a large negative contribution to the ZFS parameters. The difference in the magnitudes of the Ising-type anisotropy can be explained through ligand field theory considerations, that is, D is larger and negative in the case of weak equatorial σ-donating and strong apical π-donating ligands. To elucidate the role of intermolecular interactions in the magnetic relaxation behavior between adjacent CoII centers, a diamagnetic isostructural ZnII analog (5) was synthesized and the magnetic dilution experiment was performed.

Influence of Benzannulation on Metal Coordination Geometries: Synthesis and Structural Characterization of Tris(2-mercapto-1-methylbenzimidazolyl)hydroborato Cadmium Bromide, {[TmMeBenz]Cd(µ-Br)}2.

The tris(2-mercapto-1-methylbenzimidazolyl)hydroborato cadmium complex, {[TmMeBenz]Cd(µ-Br)}2, may be synthesized via the reaction of [TmMeBenz]K with CdBr2. X-ray diffraction demonstrates that {[TmMeBenz]Cd(µ-Br)}2 exists as a dimer, which is in marked contrast to the monomeric structure of the non-benzannulated counterpart, [TmMe]CdBr, and thereby demonstrates that benzannulation of tris(2-mercapto-1-methylbenzimidazolyl)hydroborato ligands can have a distinct impact on the molecular structure of their metal complexes. In accord with this observation, density functional theory calculations indicate that the benzannulated dimers, {[TmMeBenz]Cd(µ-X)}2 (X = Cl, Br, I), are more stable with respect to dissociation than are their non-benzannulated counterparts, {[TmMe]Cd(µ-X)}2. Furthermore, the calculations also indicate that the stability of the dimer depends on the nature of X, such that the dimer becomes more stable in the sequence I < Br < Cl.

Syntheses and crystal structures of the five- and sixfold coordinated complexes diiso-seleno-cyanato-tris-(2-methyl-pyridine N-oxide)cobalt(II) and diiso-seleno-cyanato-tetra-kis-(2-methyl-pyridine N-oxide)cobalt(II).

The reaction of CoBr2, KNCSe and 2-methyl-pyridine N-oxide (C6H7NO) in ethanol leads to the formation of crystals of [Co(NCSe)2(C6H7NO)3] (1) and [Co(NCSe)2(C6H7NO)4] (2) from the same reaction mixture. The asymmetric unit of 1 is built up of one CoII cation, two NCSe- iso-seleno-cyanate anions and three 2-methyl-pyridine N-oxide coligands, with all atoms located on general positions. The asymmetric unit of 2 consists of two cobalt cations, four iso-seleno-canate anions and eight 2-methyl-pyridine N-oxide coligands in general positions, because two crystallographically independent complexes are present. In compound 1, the CoII cations are fivefold coordinated to two terminally N-bonded anionic ligands and three 2-methyl-pyridine N-oxide coligands within a slightly distorted trigonal-bipyramidal coordination, forming discrete complexes with the O atoms occupying the equatorial sites. In compound 2, each of the two complexes is coordinated to two terminally N-bonded iso-seleno-cyanate anions and four 2-methyl-pyridine N-oxide coligands within a slightly distorted cis-CoN2O4 octa-hedral coordination geometry. In the crystal structures of 1 and 2, the complexes are linked by weak C-H⋯Se and C-H⋯O contacts. Powder X-ray diffraction reveals that neither of the two compounds were obtained as a pure crystalline phase.

Synthesis, crystal structure and properties of the trigonal-bipyramidal complex tris-(2-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II).

Reaction of Co(NCS)2 with 2-methyl-pyridine N-oxide in a 1:3 ratio in n-butanol leads to the formation of crystals of tris-(2-methyl-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), [Co(NCS)2(C6H7NO)3]. The asymmetric unit of the title compound consists of one CoII cation two thio-cyanate anions and three crystallographically independent 2-methyl-pyridine N-oxide coligands in general positions. The CoII cations are trigonal-bipyramidally coordinated by two terminal N-bonding thio-cyanate anions in the trans-positions and three 2-methyl-pyridine N-oxide coligands into discrete complexes. These complexes are linked by inter-molecular C-H⋯S inter-actions into double chains that elongate in the c-axis direction. Powder X-ray diffraction (PXRD) measurements prove that all batches are always contaminated with an additional and unknown crystalline phase. Thermogravimetry and differential analysis of crystals selected by hand reveal that the title compound decomposes at about 229°C in an exothermic reaction. At about 113°C a small endothermic signal is observed that, according to differential scanning calorimetry (DSC) measurements, is irreversible. PXRD measurements of the residue prove that a poorly crystalline and unknown phase has formed and thermomicroscopy indicates that some phase transition occurs that is accompanied with a color change of the title compound.

Crystal structure of [2-({[2-(dimethylamino-κN)ethyl]imino-κN}methyl)phenolato-κO](1,10-phen-anthroline-κ2 N,N')copper(II) perchlorate.

The title compound, [Cu(C11H15N2O)(C12H8N2)]ClO4 or [Cu(L)(phen)](ClO4) {where L refers to the deprotonated form of 2-[(2-di-methyl-amino-ethyl-imino)-meth-yl]phenol} and phen is 1,10-phenanthroline) is a mononuclear mixed ligand copper(II) complex. The CuII atom is coordinated by two N and one O atoms of the tridentate Schiff base ligand (HL) and two N atoms of the 1,10-phenanthroline ligand, resulting in a five-coordinate complex. The asymmetric unit of the title complex contains two crystallographically independent complex cations (a and b) with a slightly different geometry around the CuII ion. The value of the trigonality index τ, indicates that in both cations a and b, the CuII atoms display a square-pyramidal distorted trigonal-bipyramidal (SPDTBP) geometry, although the distortion is greater for cation a.

Di-tert-butyl-tin(IV)-hydroxide-iodide, t Bu2Sn(OH)I, the last missing member in the series of pure di-tert-butyl-tin(IV)-hydroxide-halides.

The crystal structure of di-tert-butyl-hydroxido-iodido-tin(IV), [Sn(C4H9)2I(OH)] or t Bu2Sn(OH)I, consists of dimeric, centrosymmetric mol-ecules exhibiting the typical structural features of diorganotin(IV)-hydroxide-halides, R 2Sn(OH)Hal. Two trigonal-bipyramidally coordinated tin(IV) atoms are bridged via two hydroxyl groups, resulting in a planar, four-membered {Sn-O}2 ring of rhombic shape, with acute angles at tin, obtuse angles at oxygen and two different Sn-O distances depending whether the oxygen atom adopts an axial or equatorial position at the tin(IV) atom. In contrast to its fluorine, chlorine and bromine homologues, no hydrogen bonds between the OH group and the halide atom exist, confining the inter-molecular inter-actions to van der Waals forces.

Crystal structures of zinc(II) complexes with ß-hydroxypyridinecarboxylate ligands: examples of structure-directing effects used in inorganic crystal engineering.

The coordination properties of four hydroxypyridinecarboxylates, designed for the treatment of iron-overloading conditions as bidentate O,O'-donor ligands, have been studied with ZnII in the solid state. The coordination compounds [Zn(A1)2(H2O)2] (1), [Zn(A2)2(H2O)] (2), [Zn(A3)2(H2O)]·2H2O (3) and [Zn2(B1)4(H2O)2]·4H2O (4), where the ligands are 1-methyl-4-oxidopyridinium-3-carboxylate (A1, C7H6NO3), 1,6-dimethyl-4-oxidopyridinium-3-carboxylate (A2, C8H8NO3), 1,5-dimethyl-4-oxido-pyridinium-3-carboxylate (A3, C8H8NO3) and 1-methyl-3-oxidopyridinium-4-carboxylate (B1, C7H6NO3), have been synthesized and analysed by single-crystal X-ray diffraction. The ligands were chosen to probe (i) the electronic effects of inverting the positions of the O-atom donor groups (i.e. A1 versus B1) and (ii) the electronic and steric effects of the addition of a second methyl group in different positions on the pyridine ring. Two axially coordinated water molecules resulting in a six-coordinated symmetrical octahedron complement the bis-ligand complex of A1. Ligands A2 and A3 form five-coordinated trigonal bipyramidal complexes with one additional water molecule in the coordination sphere, which is a rarely reported geometry for ZnII complexes. Ligand B1 shows a dimeric structure, where the two Zn2+ dications have slightly distorted octahedral geometry and the pyridinolate O atom of the neighbouring complex bridges them. The coordination spheres of the Zn2+ dications and the supramolecular structures are discussed in detail. The packing arrangements of 1-3 are similar, having alternating hydrophilic and hydrophobic layers, however the similarity is broken in 4. The obtained coordination geometries are compared with their previously determined CuII analogues. The study of the individual complexes is complemented with a comprehensive analysis of ZnII complexes with oxygen donor ligands with data from the Cambridge Structural Database.

Synthesis and crystal structure of NaCuIn(PO4)2.

Single crystals of sodium copper(II) indium bis-[phosphate(V)], NaCuIn(PO4)2, were grown from the melt under atmospheric conditions. The title phosphate crystallizes in the space group P21/n and is isotypic with KCuFe(PO4)2. In the crystal, two [CuO5] trigonal bipyramids share an edge to form a dimer [Cu2O8] that is connected to two PO4 tetra-hedra. The obtained [Cu2P2O12] units are inter-connected through vertices to form sheets that are sandwiched between undulating layers resulting from the junction of PO4 tetra-hedra and [InO6] octa-hedra. The two types of layers are alternately stacked along [101] and are joined into a three-dimensional framework through vertex- and edge-sharing, leaving channels parallel to the stacking direction. The channels host the sodium cations that are surrounded by four oxygen atoms in form of a distorted disphenoid.

Crystal structure of poly[[aqua-(µ-2,3-di-hydro-thieno[3,4-b][1,4]dioxine-5,7-di-carboxyl-ato-κ2O5:O7)[µ-di(pyridin-4-yl)sulfane-κ2N:N']zinc] 0.26-hydrate].

The crystal structure of the title polymer, {[Zn(C8H4O6S)(C10H8N2S)(H2O)]·0.26H2O} n , is characterized by a layered arrangement parallel to the ab plane. The zinc cation is five-coordinated in a slightly distorted trigonal-bipyramidal coordination environment defined by two pyridine ligands, two carboxyl-ate groups of two thio-phene di-carboxyl-ate ligands, and by one water mol-ecule. The ethyl-ene bridge in the dioxine ligand is disordered over two sets of sites [occupancy ratio 0.624 (9):0.376 (9)]. Several hydrogen-bonding inter-actions of the types O-H⋯O, C-H⋯O, C-H⋯S and C-H⋯N ensure the cohesion within the crystal structure.

Structure of a pentamanganese(II)-phenoxide cluster with a central five-coordinate oxide: MnII5(µ-OPh)6(µ3-OPh)2(µ5-O)(Py)6·Py (Py is pyridine).

Polynuclear metal clusters frequently feature geometric structural features not common in traditional coordination chemistry. These structures are of particular interest to bioinorganic chemists studying metallocluster enzymes, which frequently possess remarkably unusual inorganic structures. The structure of the manganese cluster µ5-oxido-di-µ3-phenoxido-hexa-µ-phenoxido-hexakis(pyridine-κN)hexamanganese(II) pyridine monosolvate, [Mn5(C6H5O)8O(C5H5N)6]·C5H5N or MnII5(µ-OPh)6(µ3-OPh)2(µ5-O)(Py)6·Py, containing an unusual trigonal bipyramidal central oxide, is described. The compound was isolated from a reaction mixture containing bis(trimethylsilylamido)manganese(II) and phenol. The central O atom is presumed to have originated as adventitious water. The molecule crystalizes in a primitive monoclinic crystal system and is presented in the centrosymetric P2/n space group. The molecule possesses crystallographically imposed twofold symmetry, with the central O atom centred on the twofold axis and surrounded by a distorted trigonal bipyramidal arrangement of Mn atoms, which are further bridged by phenoxide ligands, and terminally ligated by pyridine. A pyridine solvent molecule resides nearby, also situated on a crystallographic twofold axis. The cluster is compared to three closely related previously reported structures.

Crystal structure of a rare trigonal bipyramidal titanium(IV) coordination complex: tri-chlorido-(3,3'-di-tert-butyl-2'-hy-droxy-5,5',6,6'-tetra-methyl-1,1'-biphenyl-2-olato-κO2)(tetra-hydro-furan-κO)-titanium(IV).

The title compound, [Ti(C24H33O2)Cl3(C4H8O)], is a rare example of a trigonal-bipyramidal titanium coordination complex with three chloride and two oxygen donor ligands. The asymmetric unit contains two independent mol-ecules having essentially the same conformation. The mol-ecules feature the titanium(IV) metal cation complexed with three chloride ligands, a tetra-hydro-furan mol-ecule, and one oxygen atom from the resolved ligand precursor (R)-(+)-5,5',6,6'-tetra-methyl-3,3'-di-t-butyl-1,1'-biphenyl-2,2'-diol, where the remaining phenolic hydrogen atom engages in inter-molecular O-H⋯Cl hydrogen bonding. In one mol-ecule, the THF ligand is disordered over two orientations with refined site occupancies of 0.50 (3).

Crystal structure of (nitrato-κO)bis-(1,10'-phenanthroline-κ2N,N')copper(II) nitrate gallic acid monosolvate monohydrate.

The title compound, [Cu(NO3)(C12H8N2)2]NO3·C7H6O5·H2O, consists of a mononuclear complex cation with the central CuII atom in a distorted trigonal-bipyramidal coordination sphere. Two N atoms of two 1,10-phenanthroline ligands occupy the axial sites, and the remaining N atoms of the two ligands, as well as one nitrate O atom the equatorial positions. One mol-ecule each of gallic acid and water are present in the crystal as solvent mol-ecules that do not coordinate to the CuII cation, just as the nitrate counter-anion. In the crystal, inter-molecular O-H⋯O hydrogen bonds, as well as C-H⋯O inter-actions and π-π ring stacking between benzene and pyridine rings [centroid-to-centroid distances = 3.471 (2), 3.559 (2) and 3.790 (2) Å], link the mol-ecules into a three-dimensional network structure.

Crystal structure of the 1:1 adduct of 2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one with tri-phenyl-tin chloride.

The title adduct, chlorido-(2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one-κO)tri-phenyl-tin, [Sn(C6H5)3Cl(C16H15NOS)], resulted from reaction of 2,3-diphenyl-3,4,5,6-tetra-hydro-2H-1,3-thia-zin-4-one with tri-phenyl-tin chloride. The thia-zine ring has an envelope conformation with the S atom forming the flap. The mol-ecule has five phenyl rings, two of them attached to the thia-zine ring at positions 2 and 3, and three in coordination with the Sn(IV) atom. The three rings of the tri-phenyl-tin group are involved in intra-molecular inter-actions of different types, C-H⋯O, edge-to-face (or T-type) π-π inter-actions with the 3-phenyl ring of the thia-zine, T-type inter-actions with both phenyl rings of the thia-zine etc. On the other hand, all the phenyl rings participate in inter-molecular π-π inter-actions. There is one instance of a 'parallel-displaced'-type inter-action extending continuously along the a-axis direction and seven instances of T-type inter-actions stabilizing the crystal lattice.

Crystal structure of {6,6'-dihy-droxy-2,2'-[imino-bis-(propane-1,3-diyl-nitrilo-methanylyl-idene)]diphenolato-κ(5) O (1),N,N',N'',O (1')}copper(II).

The title compound, [Cu(C20H23N3O4)], crystallizes in the space group Cc with two independent mol-ecules in the asymmetric unit. The Cu(II) atoms are each coordinated by the penta-dentate Schiff base ligand in a distorted trigonal bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O atoms and the amine N atom, while the axial positions are occupied by the two imine N atoms. In the crystal, the two independent mol-ecules are each connected into a column along the b axis through inter-molecular O-H⋯O hydrogen bonds. The two independent columns are further linked through an N-H⋯O hydrogen bond, forming a double-column structure.

Five Stereoactive Orbitals on Silicon: Charge and Spin Localization in the n-Si4Me10(-•) Radical Anion by Trigonal Bipyramidalization.

RIUMP2/def2-TZVPPD calculations show that in addition to its usual conformation with charge and spin delocalized over the Si backbone, the isolated Si4Me10(-•) radical anion also has isomeric conformations with localized charge and spin. A structure with localization on a terminal Si atom has been examined in detail. In vacuum, it is calculated to lie 11.5 kcal/mol higher in energy than the charge-and-spin delocalized conformation, and in water the difference is as little as 1.6 kcal/mol. According to natural orbital and localized orbital analyses, the charge-and-spin-carrying terminal Si atom uses five stereoactive hybrid orbitals in a trigonal bipyramidal geometry. Four are built mostly from 3s and 3p atomic orbitals (AOs) and are used to attach a Si3(CH3)7 and three CH3 groups, whereas the larger equatorial fifth orbital is constructed from 4s and 4p AOs and acts as a nonbonding (radical) hybrid orbital with an occupancy of about 0.65 e.