Showing papers in "Inorganic Chemistry in 1998"
TL;DR: The role of the lone pair of electrons of Pb(II) in determining the coordination geometry is analyzed from crystallographic studies and ab initio molecular orbital optimizations in this article, where factors that contribute to the disposition of ligands around the lead with geometries that are: (1) holodirected, in which the bonds to ligand atoms are distributed throughout the surface of an encompassing globe, and (2) hemidirected (i.e., there is an identifiable void in the distribution of bonds to the ligands).
Abstract: The role of the lone pair of electrons of Pb(II) in determining the coordination geometry is analyzed from crystallographic studies and ab initio molecular orbital optimizations. Of particular interest are factors that contribute to the disposition of ligands around the lead with geometries that are (1) holodirected, in which the bonds to ligand atoms are distributed throughout the surface of an encompassing globe, and (2) hemidirected, in which the bonds to ligand atoms are directed throughout only part of an encompassing globe, i.e., there is an identifiable void in the distribution of bonds to the ligands. The preferred coordination numbers for lead were found to be 4 for Pb(IV) and 4 and 6 for Pb(II). All Pb(IV) structures in the CSD have a holodirected coordination geometry. Pb(II) compounds are hemidirected for low coordination numbers (2−5) and holodirected for high coordination numbers (9, 10), but for intermediate coordination numbers (6−8), examples of either type of stereochemistry are found. A...
845 citations
TL;DR: This work developed a general methodology and a general computational tool, which identifies the minimal distance of a given structure to a desired general shape with the same number of vertexes, and employs this tool to evaluate quantitatively the degree of polyhedricity within distorted polyhedra.
Abstract: The continuous symmetry measures approach, designed to assess quantitatively the degree of any symmetry within any structure, is extended to the important class of the polyhedra. For this purpose, we developed a general methodology and a general computational tool, which identify the minimal distance of a given structure to a desired general shape with the same number of vertexes. Specifically, we employ this tool to evaluate quantitatively the degree of polyhedricity within distorted polyhedra, taking as examples the most central and abundant polyhedral structures in chemistry in general and in coordination chemistry in particular, namely the tetrahedron, the bipyramid, the octahedron, the cube, the icosahedron, and the dodecahedron. After describing the properties of the symmetry measurement tool, we show its application and versatility in a number of cases where the deviation from exact symmetry has been an issue, including z-axis Jahn−Teller type polyhedral distortions, tantalum hydride complexes, pen...
602 citations
TL;DR: In this article, the interaction of copper(II/I) complexes of a few 2,9-dimethyl-1,10-phenanthrolines with calf thymus DNA has been investigated using absorption and circular dichroic spectral and electrochemical techniques and viscometry.
Abstract: The interaction of copper(II/I) complexes of a few 2,9-dimethyl-1,10-phenanthrolines with calf thymus DNA has been investigated using absorption and circular dichroic spectral and electrochemical techniques and viscometry. The observation of the usual hypochromism and the novel hyperchromism in the absorption spectra of [CuI(bcp)2]+ [bcp = 2,9-dimethyl-4,7-diphenyl-1,10- phenanthroline] and [CuI(dpsmp)2]3- [dpsmp2- = 2,9-dimethyl-4,7-bis(sulfonatophenyl)-1,10-phenanthroline] respectively in the presence of DNA and the increase in viscosity of DNA at low loadings of both these complexes have been interpreted in terms of bridging of a pair of DNA duplexes by the complex species. These tetrahedral copper(I) complexes, which lack minor groove binding because of substituents at the 4- and 7-positions of phen ring, are efficient in bridging the duplexes. The electrochemical behaviors of [CuI(dmp)2]+ [dmp = 2,9-dimethyl-1,10-phenanthroline] and [CuI(bcp)2]+ bound to DNA have been compared with that of the analog...
362 citations
TL;DR: The new spin-crossover compound Fe(PM- biA)(2)(NCS)(2) with PM-BiA = N-(2-pyridylmethylene)aminobiphenyl has been synthesized and the determination of the intermolecular contacts in the LS and HS forms has revealed a two-dimensional structural character.
Abstract: The new spin-crossover compound Fe(PM-BiA)2(NCS)2 with PM-BiA = N-(2-pyridylmethylene)aminobiphenyl has been synthesized. The temperature dependence of χMT (χM = molar magnetic susceptibility and T...
350 citations
TL;DR: The complex [Ru(NH3)4dppz]2+ showed a metal to ligand charge transfer (MLCT) transition at ∼544 nm but does not show any photoluminescence.
Abstract: The complex [Ru(NH3)4dppz]2+ shows a metal to ligand charge transfer (MLCT) transition at ∼544 nm but does not show any photoluminescence. The complex does not exhibit any solvent-dependent MLCT changes, unlike its bpy and phen counterparts. The complex showed intercalative binding to calf thymus DNA that was weaker than [Ru(phen)2dppz]2+.
306 citations
TL;DR: NMR data clearly indicate that Δ-[Ru(phen)2dpq]2+ binds the hexanucleotide d(GTCGAC)2 by intercalation, of the dpq ligand, from the minor groove, and demonstrates that metallointercalators can intercalate from the DNA minor groove.
Abstract: 1H NMR spectroscopy was used to study the oligonucleotide binding of the Δ enantiomers of [Ru(phen)2L]2+ where the bidentate ligand L is 1,10-phenanthroline (phen), dipyrido[3,2-d:2‘,3‘-f]quinoxaline (dpq) or dipyrido[3,2-a:2‘,3‘-c](6,7,8,9-tetrahydro)phenazine (dpqC). The data from one- and two-dimensional NMR experiments of the oligonucleotide−metal complex binding suggest that all three ruthenium(II) polypyridyl complexes bind in the DNA minor groove. While a minimally intercalated oligonucleotide binding mode may be proposed for Δ-[Ru(phen)3]2+, the NMR data clearly indicate that Δ-[Ru(phen)2dpq]2+ binds the hexanucleotide d(GTCGAC)2 by intercalation, of the dpq ligand, from the minor groove. This demonstrates that metallointercalators can intercalate from the DNA minor groove. Molecular modeling of the metal complex in the intercalation site suggests that Δ-[Ru(phen)2dpq]2+ binds in a “head-on” fashion with the phenanthroline rings in the minor groove and the dpq ligand inserted into the nucleotide b...
305 citations
TL;DR: Equations are derived and discussed that allow the computation of zero-field splitting (ZFS) tensors in transition metal complexes for any value of the ground-state total spin S that includes contributions from excited states of spin S and S +/- 1.
Abstract: Equations are derived and discussed that allow the computation of zero-field splitting (ZFS) tensors in transition metal complexes for any value of the ground-state total spin S. An effective Hamiltonian technique is used and the calculation is carried to second order for orbitally nondegenerate ground states. The theory includes contributions from excited states of spin S and S ± 1. This makes the theory more general than earlier treatments. Explicit equations are derived for the case where all states are well described by single-determinantal wave functions, for example restricted open shell Hartree−Fock (HF) and spin-polarized HF or density functional (DFT) calculation schemes. Matrix elements are evaluated for many electron wave functions that result from a molecular orbital (MO) treatment including configuration interaction (CI). A computational implementation in terms of bonded functions is outlined. The problem of ZFS in high-spin ferric complexes is treated at some length, and contributions due to...
291 citations
TL;DR: Kinetic experiments show that [Cu(2)(L-55)](4+) is the most efficient catalyst (rate constant 140 M(-1) s(-1)), followed by [Cu (2)(LB5)]( 4+) (60 M(- 1) s (-1)), in this oxidation, while [ Cu(2(L-66)] (4+) undergoes an extremely fast stoichiometric phase followed by a slow and substrate-concentration-independent catalytic phase.
Abstract: The dicopper(II) complex with the ligand N,N,N‘,N‘,N‘‘-pentakis[(1-methyl-2-benzimidazolyl)methyl]dipropylenetriamine (LB5) has been synthesized and structurally characterized. The small size and the quality of the single crystal required that data be collected using synchrotron radiation at 276 K. [Cu2(LB5)(H2O)2][ClO4]4: platelet shaped, P1, a = 11.028 A, b = 17.915 A, c = 20.745 A, α = 107.44°, β = 101.56°, γ = 104.89°, V = 3603.7 A3, Z = 2; number of unique data, I ≥ 2σ(I) = 3447; number of refined parameters = 428; R = 0.12. The ligand binds the two coppers nonsymmetrically; Cu1 is coordinated through five N donors and Cu2 through the remaining three N donors, while two water molecules complete the coordination sphere. Cu1 has distorted TBP geometry, while Cu2 has distorted SP geometry. Voltammetric experiments show quasireversible reductions at the two copper centers, with redox potential higher for the CuN3 center (0.40 V) and lower for the CuN5 center (0.17 V). The complex binds azide in the ter...
277 citations
TL;DR: In this article, various mechanisms to explain negative thermal expansion in oxides are presented, focusing on the mechanism based on transverse thermal motion of oxygen in M−O−M linkages.
Abstract: Various mechanisms to explain negative thermal expansion in oxides are presented. Our search for compounds having this unusual property has focused on the mechanism based on transverse thermal motion of oxygen in M−O−M linkages. Such a mechanism can give strong negative thermal expansion over broad temperature ranges. Examples of compounds where this mechanism operates to give negative thermal expansion are ZrW2O8, the Sc2W3O12 family, NbOPO4, AlPO4-17, and faujasite SiO2.
258 citations
TL;DR: The results suggest that the guest 2, 4'-bpy molecules and protonated [4,4'-H(2)bpy](2+) cations present in the reaction systems serve as structure-directing templates in the formation of the crystal structures and exclude self-inclusion of the networks having larger square cavities.
Abstract: In the presence of guest 2,4'-bpy molecules or under acidic conditions, three compounds, [Cd(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (1), [Zn(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(2).(2,4'-bpy)(2).H(2)O (2), and [Cu(4,4'-bpy)(2)(H(2)O)(2)](ClO(4))(4).(4,4'-H(2)bpy) (3), were obtained from the reactions of the metal salts and 4,4'-bpy in an EtOH-H(2)O mixture. 1 has a 2-D square-grid network structure, crystallizing in the monoclinic space group P2/n, with a = 13.231(3) A, b = 11.669(2) A, c = 15.019(3) A, beta = 112.82(3) degrees, Z = 2; 2 is isomorphous with 1, crystallizing in the monoclinic space group P2/n, with a = 13.150(3) A, b = 11.368(2) A, c = 14.745(3) A, beta = 110.60(3) degrees, Z = 2. The square grids superpose on each other into a channel structure, in which each layer consists of two pairs of shared edges, perfectly square-planar with an M(II) ion and a 4,4'-bpy at each corner and side, respectively. The square cavity has dimensions of 11.669(2) x 11.788(2) and 11.368(2) x 11.488(2) A for 1 and 2, respectively. Every two guest 2,4'-bpy molecules are clathrated in each hydrophobic host cavity and are further stabilized by pi-pi stacking and hydrogen bonding interactions. The NMR spectra clearly confirm that both 1 and 2 contain 4,4'-bpy and 2,4'-bpy molecules in a 1:1 ratio, which have stacking interaction with each other in the solution. 3 crystallizes in the orthorhombic space group Ibam, with a = 11.1283(5) A, b = 15.5927(8) A, c = 22.3178(11) A, Z = 4. 3 is made up of two-dimensional square [Cu(4)(4,4'-bpy)(4)] grids, where the square cavity has dimensions of 11.13 x 11.16 A. Each [4,4'-H(2)bpy](2+) cation is clathrated in a square cavity and stacks with one pair of opposite edges of the host square cavity in an offset fashion with the face-to-face distance of ca. 3.95 A. Within each cavity, the [4,4'-H(2)bpy](2+) cation forms twin three-center hydrogen bonds with two pairs of ClO(4)(-) anions. The results suggest that the guest 2,4'-bpy molecules and protonated [4,4'-H(2)bpy](2+) cations present in the reaction systems serve as structure-directing templates in the formation of the crystal structures and exclude self-inclusion of the networks having larger square cavities.
257 citations
TL;DR: A series of PtIV anticancer complexes with chloro leaving groups have been investigated for the effects of axial and carrier ligands on the reduction and cytotoxicity as discussed by the authors, and the reduction rates of the PtIV complexes such as Pt(d,l), 1,2-(NH2)2C6H10)Cl4 (tetraplatin, Pt(m,dach), Pt(n),1,2(NH2)(OCOCH3)2Cl2] (m = diaminocyclohexane), cis,trans,
Abstract: A series of PtIV anticancer complexes with chloro leaving groups have been investigated for the effects of axial and carrier ligands on the reduction and cytotoxicity. The reduction rates of the PtIV complexes such as Pt(d,l)(1,2-(NH2)2C6H10)Cl4 (tetraplatin, Pt(dach)Cl4; dach = diaminocyclohexane), cis,trans,cis-[Pt((CH3)2CHNH2)2(OH)2Cl2] (iproplatin, Pt(ipa)(OH)2Cl2; ipa = isopropylamine), cis,trans,cis-[Pt(NH3)(C6H11NH2)(OCOCH3)2Cl2] (JM-216, Pt(a,cha)(OCOCH3)2Cl2; a = ammine, cha = cyclohexylamine), cis,trans,cis-[Pt(NH3)(C6H11NH2)(OCOC3H7)2Cl2] (JM-221, Pt(a,cha)(OCOC3H7)2Cl2), cis,trans,cis-[Pt(en)(OH)2Cl2], Pt(en)Cl4 (en = ethylenediamine), cis,trans,cis-[Pt(en)(OCOCH3)2Cl2], and cis,trans,cis-[Pt(en)(OCOCF3)2Cl2] by ascorbate and cathodic reduction potentials strongly depend on the electron-withdrawing power and the steric hindrance of the axial and carrier ligands. Beginning with PtIV complexes bearing en carrier ligands, reduction rates and reduction potentials increase in the following order of...
TL;DR: In this paper, the binding energy of the Au(Xe)+ complex has been studied comprehensively by CCSD(T) calculations in order to provide a benchmark for a gold(I) cation affinity scale.
Abstract: Ligation of atomic gold(I) cation Au+ by various inorganic and organic ligands containing heteroatoms has been examined by experimental and theoretical means The Au(Xe)+ complex has been studied comprehensively by CCSD(T) calculations in order to provide a benchmark for a gold(I) cation affinity scale The best theoretical estimate of the binding energy is D0(Au+−Xe) = 301 kcal/mol This value is used to relate calculated and experimentally bracketed binding energies of Au(L)+ complexes with a relative gold(I) cation affinity scale for heteroatom ligands L, ie, Xe < C6F6 < H2O < CO < H2S < CH3CN ≈ C2H4 ≈ NH3 ≈ CH3NC < CH3SCH3 < PH3 In comparison to other transition metal cations, the gold(I) cation is unique in that the binding energies to several ligands are exceptionally large Further, the covalent character of the Au+−L bonds as well as charge transfer from the ligand to gold are significant Finally, the gas-phase behavior of Au+ suggests some implications for possible new approaches to gold(I)
TL;DR: In this paper, a comprehensive ab initio calculation on the closo-monocarbaboranes, CBn-1Hn- (n = 5−12), and closo -dicarboranes, C2Bn-2Hn (n= 5− 12), showed that the relative energies of all the positional isomers agree with the qualitative connectivity considerations of Williams and with the topological charge stabilization rule of Gimarc.
Abstract: Comprehensive ab initio calculations RMP2(fc)/6-31G* on the closo-monocarbaboranes, CBn-1Hn- (n = 5−12), and the closo-dicarboranes, C2Bn-2Hn (n = 5−12), show that the relative energies of all the positional isomers agree with the qualitative connectivity considerations of Williams and with the topological charge stabilization rule of Gimarc. The reaction energies (ΔH) of the most stable positional isomers, 1-CB4H5-, CB5H6-, 2-CB6H7-, 1-CB7H8-, 5-CB8H9-, 1-CB9H10-, 2-CB10H11-, CB11H12-, as well as 1,5-C2B3H5, 1,6-C2B4H6, 2,4-C2B5H7, 1,7-C2B6H8, 4,5-C2B7H9, 1,10-C2B8H10, 2,3-C2B9H11, and 1,12-C2B10H12 (computed using the equations, CBH2- + (n − 1)BHincrement → CBnHn+1- (n = 4−11) and C2H2 + nBHincrement → C2BnHn+2 (n = 3−10)), show that the stabilities of closo-CBn-1Hn- and of closo-C2Bn-2Hn generally increase with increasing cluster size from 5 to 12 vertexes. This is a characteristic of three-dimensional aromaticity. There are variations in stabilities of individual closo-CBn-1Hn- and closo-C2Bn-2Hn spec...
TL;DR: The data in this study suggest the significance of ligand-unsupported silver-silver interactions (argentophilicity) in Tl[Ag(CN)(2)].
Abstract: The structure of thallium dicyanoargentate(I) has been determined crystallographically. The crystal structure shows an Ag−Ag distance of 3.11 A. This is the shortest Ag−Ag distance reported for any silver dicyanide salt whose crystal structure has been determined. Raman spectra of the compound show four νC-N peaks that are well-resolved in the 10−80 K temperature range. This result agrees well with group theory analysis. Extended Huckel calculations using relativistic wave functions have been carried out for two models which describe the interactions between the Ag(CN)2- ions within the crystal structure of Tl[Ag(CN)2]. The results of these calculations indicate the formation of potential wells at short Ag−Ag distances. The data in this study suggest the significance of ligand-unsupported silver−silver interactions (argentophilicity) in Tl[Ag(CN)2]. Tl−Ag interactions are determined to be insignificant in the compound. Tl[Ag(CN)2] crystallizes in the monoclinic space group P21/c (No. 14), with a = 7.798(1...
TL;DR: In this article, two solvent-dependent structures of Co(NO3)2 with trans-1,2-bis(4-pyridyl)ethylene (bpee) and their interconversions were analyzed.
Abstract: Studies have been carried out on two solvent-dependent structures of Co(NO3)2 with trans-1,2-bis(4-pyridyl)ethylene (bpee) and their interconversions. X-ray analyses disclose that the molecule obta...
TL;DR: These photophysical studies establish a sequence preference in binding to DNA by Ru(phen)(2)dppz(2+) as well as providing support for the original assignment by NMR of ruthenium intercalation from the major groove side of the DNA helix.
Abstract: Emission of Δ-Ru(phen)_2dppz^(2+) bound to nucleic acid polymers of different sequence has been investigated by time-resolved luminescence spectroscopy and the effect of major and minor groove DNA binding agents on the luminescence profile of the complex evaluated. In the presence of a 1:1 mixture of poly d(AT) and poly d(GC), the excited-state decay of Δ-Ru(phen)_2dppz^(2+) can be described by a linear combination of the decay profiles in the presence of poly d(AT) and poly d(GC) independently. This analysis indicates that ∼85% of the complexes are bound to poly d(AT) and that the metallointercalator preferentially occupies AT sites in mixed-sequence polymers such as calf thymus or T4 DNA. When rac-Ru(phen)_2dppz^(2+) bound to [d(5‘-GAGTGCACTC-3‘)_2] is titrated with the major groove intercalator Δ-α-[Rh[(R,R)-Me_2trien]phi]^(3+), the ruthenium emission yield decreases while the absorbance of the π−π^* transition centered on the dppz ligand increases, until saturation behavior is observed at a 1:1 Rh/duplex ratio. These titrations indicate that Ru(phen)_2dppz^(2+) is displaced from the major groove by the rhodium complex. In contrast, for rac-Ru(phen)_2dppz^(2+) bound to poly d(AT), addition of the minor groove binding agent distamycin produces an increase in ruthenium emission which saturates at ∼1 distamycin/5 bp, consistent with the double helix being able to accommodate major and minor groove binders simultaneously. Distamycin has no effect on the emission of Ru(phen)_2dppz^(2+) emission bound to poly d(GC). These photophysical studies establish a sequence preference in binding to DNA by Ru(phen)_2dppz^(2+) as well as providing support for the original assignment by NMR of ruthenium intercalation from the major groove side of the DNA helix.
TL;DR: Several new ligands, azoimidazoles belonging to the class 1-methyl-2-(arylazo)imidazesoles (L1 (3)) and 1-benzyl-2-arylazo (L2 (4)) (R = H (a), Me (b), OMe (c), Cl (d), NO2 (e)) have been synthesized and reacted with RuCl3 in ethanol under refluxing conditions.
Abstract: Several new ligands, azoimidazoles belonging to the class 1-methyl-2-(arylazo)imidazoles (L1 (3)) and 1-benzyl-2-(arylazo)imidazoles (L2 (4)) (R = H (a), Me (b), OMe (c), Cl (d), NO2 (e)) have been synthesized and reacted with RuCl3 in ethanol under refluxing conditions. Two isomers of the composition RuL2Cl2, green (i) and blue (iii), are chromatographically separated. The green isomer is quantitatively transformed to the blue isomer on refluxing in a high boiling solvent. The isomeric structures have been confirmed by X-ray crystallography. Crystal data are as follows. Green complex C38H34Cl2N8Ru (6a): crystal system monoclinic; space group C2/c; a = 15.680(8) A; b = 22.766(14) A; c = 11.473(5) A; β = 119.27(4)°; V = 3573(3) A3 Z = 4; R = 3.59%; Rw = 4.38%. Blue complex C22H24Cl2N8Ru (7b): crystal system monoclinic; space group P21/n, a = 9.547(6) A; b = 22.554(14) A; c = 11.748(8) A; β = 99.07(5)°; V = 2498(3) A3; Z = 4; R = 3.15%; Rw = 4.51%. With reference to the pairs of Cl, N(imidazole), and N(az...
TL;DR: In this article, the dependence of the intramolecular MI−MI interaction on electron correlation effects in eight-membered rings of type [M2(PH2CH2PH2)2]2+, [M 2(NHCHNH)2], [M = Au, Ag, Cu), [Au2...
Abstract: We study the dependence of the intramolecular MI−MI interaction on electron correlation effects in eight-membered rings of type [M2(PH2CH2PH2)2]2+, [M2(NHCHNH)2], [M2(SCHS)2] (M = Au, Ag, Cu), [Au2...
TL;DR: In this paper, the self-assembly of AgX (X = NO3-, ClO4-) with 2,4-bipyridine (2,4‘-bpy) was studied.
Abstract: Two compounds, [Ag(2,4‘-bpy)]NO3 (1) and [Ag(2,4‘-bpy)]ClO4 (2), were obtained from self-assembly of AgX (X = NO3-, ClO4-) with 2,4‘-bipyridine (2,4‘-bpy). 1 crystallizes in the orthorhombic space group Pbca, with a = 11.2884(7) A, b = 11.3981(10) A, c = 16.5299(13) A, and Z = 8, while 2 crystallizes in the monoclinic space group P21/c, with a = 10.6361(4) A, b = 9.9896(4) A, c = 11.2661(6) A, β = 98.527(4)°, and Z = 4. Both complexes consist of helical [Ag(2,4‘-bpy)]∞ chains that are surrounded by nitrate or perchlorate counterions. Adjacent helical chains are racemic. The AgI atom is linked to two nitrogen atoms of the 2-pyridyl and 4‘-pyridyl groups from two different 2,4‘-bpy ligands as well as to the oxygen atom of the counterion. In 1, another oxygen atom of the counterion is weakly coordinated to the AgI atom of an adjacent chain, thus bridging the helical chains into a wavy 2-D network structure, whereas in 2, adjacent helical chains are linked by the weak ligand-unsupported metal−metal interactio...
TL;DR: The structure and dehydration behavior of the porous 3D coordination polymer {[La2(adipate)3(H2O)4]6H 2O}n are described in this article.
Abstract: The structure and dehydration behavior of the porous 3D coordination polymer {[La2(adipate)3(H2O)4]6H2O}n are described. Each La3+ is coordinated by nine oxygen atoms belonging to five carboxylate ...
TL;DR: In this paper, the emission spectra of EuIII β-diketone complexes were analyzed and it was shown that the Na[Eu(L)2] complexes exhibit higher quantum yields than the corresponding Eu2L3 species, and that luminescence is negligible when the ligand triplet-state lies below the 5Do state of the euIII.
Abstract: New EuIII Schiff base compounds and polyelectrolytes luminesce with quantum yields consistent with the intramolecular energy transfer mechanism established for EuIII β-diketone complexes. The emission spectra clearly show that the two EuIII ions in Eu2L3 complexes, where L is a tetradentate Schiff base ligand, are in different environments, that the Na[Eu(L)2] complexes exhibit higher quantum yields than the corresponding Eu2L3 species, and that luminescence is negligible when the ligand triplet-state lies below the 5Do state of EuIII.
TL;DR: Solution-state absorption and (1)H NMR spectra indicate that the [Cu(dpp)(2)](+) complex is fluxional in solution, rocking between two enantiomeric structures of C(2) molecular symmetry through an intermediate ofC(s)() symmetry.
Abstract: The syntheses, crystal structures, and electronic absorption spectra of the copper(I) and copper(II) complexes of 2,9-diphenyl-1,10-phenanthroline (dpp) are reported. The complex [Cu(dpp)2](PF6) (1) crystallizes in space group P21/c with a = 11.081(4) A, b = 25.491(8) A, c = 14.263(5) A, β = 92.84(3)°, Z = 4, and V = 4024(2) A3. For 4813 unique data with F > 4.0σ(F), R = 5.41% and Rw = 6.43%. The coordination geometry about the copper(I) center in [Cu(dpp)2]+ is best described as distorted tetrahedral with approximate C2 symmetry. The structure of [Cu(dpp)2]+ is largely determined by interligand π-stacking interactions that occur between the phenyl groups of one ligand and the phenanthroline moiety of the other ligand. Solution-state absorption and 1H NMR spectra indicate that the [Cu(dpp)2]+ complex is fluxional in solution, rocking between two enantiomeric structures of C2 molecular symmetry through an intermediate of Cs symmetry. The complex [Cu(dpp)2](ClO4)2 (2) crystallizes in space group P1 with a ...
TL;DR: A series of new organometallic platinum(II) complexes containing terdentate polypyridine ligands has been prepared and characterized and NMR data evidence that all the complexes but 3 and 6 oligomerize in solution leading to stacked species.
Abstract: A series of new organometallic platinum(II) complexes containing terdentate polypyridine ligands has been prepared and characterized. Their absorption spectra in 4:1 (v/v) MeOH/EtOH fluid solution at room temperature and luminescence in the same matrix at 77 K have been investigated. The new species are [Pt(terpy)Ph]Cl (3, terpy = 2,2‘:6‘,2‘‘-terpyridine, Ph = phenyl), [Pt(Ph-terpy)Cl]Cl (4, Ph-terpy = 4‘-phenyl-2,2‘:6‘,2‘‘-terpyridine), [Pt(Ph-terpy)Me]Cl (5), and [Pt(Ph-terpy)Ph]Cl (6). The results have been compared with those for [Pt(terpy)Cl]Cl (1) and [Pt(terpy)Me]Cl (2). NMR data evidence that all the complexes but 3 and 6 oligomerize in solution leading to stacked species. The absorption spectra are dominated by moderately intense metal-to-ligand charge-transfer (MLCT) bands in the visible region and by intense ligand-centered (LC) bands in the UV region. All the compounds are luminescent in a 4:1 (v/v) MeOH/EtOH rigid matrix at 77 K, exhibiting a structured emission within the range 460−600 nm. T...
TL;DR: In this article, neutral isoelectronic molecules AB = N2, CO, BF, and SiO and their coordination in the model complexes Fe(CO)4AB and Fe(AB)5, using nonlocal density functional theory and a large, polarized STO basis set of triple-ζ quality (NL-SCF/TZ(2P)).
Abstract: Carbon monoxide, CO, is a ubiquitous ligand in organometallic and coordination chemistry. In the present paper we investigate the neutral isoelectronic molecules AB = N2, CO, BF, and SiO and their coordination in the model complexes Fe(CO)4AB and Fe(AB)5, using nonlocal density functional theory and a large, polarized STO basis set of triple-ζ quality (NL-SCF/TZ(2P)). Our aim is to get more insight into the ligating properties of SiO and BF in comparison to CO and N2. The computed 298 K Fe(CO)4−AB bond dissociation enthalpies of C3v-symmetric Fe(CO)4AB are 18.1, 42.3, 67.9, and 35.6 kcal/mol for N2, CO, BF, and SiO, respectively; the corresponding values for C2v-symmetric Fe(CO)4AB are comparable: 19.0, 42.3, 66.7, and 39.7 kcal/mol. Good, balanced σ donation (through 5σ) and π acceptance (through 2π) are what makes CO a good donor, of course. The gap between these frontier orbitals (5σ and 2π) becomes even smaller in SiO and BF. The analysis of the bonding mechanism of the Fe−AB bond shows that SiO is a...
TL;DR: In this article, a binuclear binuclear unit was characterized by X-ray analysis. But the complexity of the Binuclear Binuclear Unit (BINU) was not characterized.
Abstract: [Mn(BS)(H2O)]ClO4 and [NEt4]3[Fe(CN)6] react in methanol or ethanol to give a binuclear [NEt4]2[{Mn(BS)(S)}{Fe(CN)6}], 1, three trinuclear [NEt4][{Mn(BS)(S)}2{Fe(CN)6}], 2−4, and a pentanuclear [Mn(BS)(S)]4[Fe(CN)6]ClO4, 5, heterometal complex, depending on the nature of the quadridentate Schiff-base ligands and regardless of the stoichiometric ratio of the precursor components (BS = saldmen = N,N‘-(1,1-dimethylethylene)bis(salicylideneiminato) dianion, S = H2O for 1; BS = rac-salmen = rac-N,N‘-(1-methylethylene)bis(salicylideneiminato) dianion, S = MeOH for 2; BS = rac-salcy = rac-N,N‘-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion, S = MeOH for 3; (R,R)-salcy = (R,R)-N,N‘-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion, S = H2O for 4; BS = saltmen = N,N‘-(1,1,2,2-tetramethylethylene)bis(salycylideneiminato) dianion, S = H2O for 5). Complexes 1 and 2 have been characterized by X-ray analyses. Complex 1 consists of a discrete CN-bridged Mn(III)−Fe(III) binuclear unit [(H2O)Mn(...
TL;DR: The results of single-crystal structural analyses of two representative compounds within the isostructural series are discussed in this paper, where the crystal structures assume extended molecular arrays based on two types of symmetrically independen...
Abstract: Reaction of tris(oxalato)chromium(III) complexes, [CrIII(ox)3]3- (ox2- = C2O42-), with salts of the trivalent rare earth ions, Ln = La, Ce, Pr, and Nd, generates the polymeric 3d−4f coordination solids with stoichiometries [LnIIICrIII(ox)3(H2O)4]2·nH2O, n varies from 12 to 7. Results of single-crystal structural analyses of two representative compounds within the isostructural series are discussed. Crystal data: [LaIIICrIII(ox)3(H2O)4]2· 12H2O (1), monoclinic, space group C2, a = 36.080(8) A, b = 10.906(1) A, c = 10.935(2) A, β = 105.55(1)°, Z = 4; [CeIIICrIII(ox)3(H2O)4]2·12H2O (2), monoclinic, space group C2, a = 36.075(6) A, b = 10.887(1) A, c = 10.913(2) A, β = 105.65(1)°, Z = 4. X-ray powder diffraction established the isostructurality within the series, and from thermal gravimetry analyses, the number of water molecules of crystallization for the conditioned, polycrystalline samples was determined. The crystal structures assume extended molecular arrays based on two types of symmetrically independen...
TL;DR: In this article, the authors report the synthesis and structure and discuss in substantial detail the bonding of a remarkable family of compounds spanning most of the transition series, which were previously unknown, crystallizes in the TiNiSi structure type.
Abstract: We report the synthesis and structure and discuss in substantial detail the bonding of a remarkable family of compounds spanning most of the transition series. All members of the MTSi (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni; T = Co, Ni) series have now been prepared, and their crystal structures have been determined accurately using X-ray diffraction and, for MnNiSi and FeNiSi, neutron diffraction. Each of these compounds, four of which were previously unknown, crystallizes in the TiNiSi structure type. In contrast, for T = Cu, one has only representatives with M = Sc and Ti. A simple Zintl picture, which works so well for the three-dimensional four-connected indium net of the related BaIn2 structure, is not applicable to these intermetallics; there is substantial M−T and M−Si bonding, and the “extra” electrons in the MTSi structure enter orbitals essentially nonbonding within the TSi network. A structural change observed for M = Fe and higher d-electron counts, distorting the six-rings in the structure, is tr...
TL;DR: In this article, a two-dimensional material constructed from molybdenum oxide chains linked through hydrogen bonding of the protonated, pendant arms of the Hbpa+ ligand was presented.
Abstract: The hydrothermal reaction of MoO3 and 4,4‘ -bipyridylamine yields [Mo4O13(Hbpa)2], a two-dimensional material constructed from molybdenum oxide chains linked through hydrogen bonding of the protonated, pendant arms of the Hbpa+ ligand.
TL;DR: In this paper, the self-assembly of silver salts and the bidentate pyridazine (pydz) was used to obtain helical coordination polymers from the selfassembly of pyridine.
Abstract: Helical coordination polymers have been obtained from the self-assembly of silver salts and the bidentate pyridazine (pydz), which include [Ag(pydz)](NO3), [Ag(pydz)](CF3SO3), containing 21 helices of different periods, and the unusual 41 helical species [Ag(pydz)2](BF4).
TL;DR: The preparation, crystal structures, and variable temperature magnetic susceptibility data are presented for two azido-bridged Schiff base complexes of Mn(III) and Fe(III).
Abstract: The preparation, crystal structures, and variable temperature magnetic susceptibility data are presented for two azido-bridged Schiff base complexes of Mn(III) and Fe(III). Mn(salpn)N3 (1), where s...