Metal Coordination Compounds Research Articles

ChemInform Abstract: Coordination Equilibria and Coupling Reactions of Unsaturated Hydrocarbons at a Metal Centre

The field of hydrocarbon catalysis has been an area of intensive research and major progress in recent years attributed to the remarkable catalytic effect of various types of transition metal coordination compounds. Although the interaction of saturated hydrocarbons with some metal complexes has recently attracted interest, unsaturated hydrocarbons have much more important scientific as well as industrial aspects. This review therefore summarizes recent views of some of the fundamental chemical processes resulting from the interactions of unsaturated hydrocarbons with metal species

Sparkle/PM6 Parameters for all Lanthanide Trications from La(III) to Lu(III).

PM6 is the first semiempirical method to be released already parametrized for the elements of the periodic table, from hydrogen to bismuth (Z = 83), with the exception of the lanthanides from cerium (Z = 58) to ytterbium (Z = 70). In order to fill this gap, we present in this article a generalization of our Sparkle Model for the quantum chemical semiempirical calculation of lanthanide complexes to PM6. Accordingly, we present Sparkle/PM6 parameters for all lanthanide trications from La(III) to Lu(III). The validation procedure again considered only high-quality crystallographic structures and included 633 complexes. Sparkle/PM6 unsigned mean errors UME(Ln-L)s, corresponding to all the interatomic distances between the lanthanide ion and the atoms directly coordinated to it, range from 0.066 to 0.086 Å for Gd(III) and Ce(III), respectively. These minimum and maximum UME(Ln-L)s across the lanthanide series are comparable to the Sparkle/AM1 values of 0.054 and 0.085 Å for Ho(III) and Pr(III), respectively, as well as to the values for Sparkle/PM3 of 0.064 and 0.093 Å for Gd(III) and Pr(III), respectively. Moreover, for all 15 lanthanide ions, these interatomic distance deviations follow a γ distribution within a 95% level of confidence, indicating that these errors appear to be random around a mean, freeing the model of systematic errors, at least within the validation set. Sparkle/PM6 presented here, therefore, broadens the range of applicability of PM6 to the coordination compounds of the rare earth metals.

Discovery of New Ferroelectrics: [H2dbco]2·[Cl3]·[CuCl3(H2O)2]·H2O (dbco = 1,4-Diaza-bicyclo[2.2.2]octane)

Compound [H(2)dbco](2) x [Cl(3)] x [CuCl(3)(H(2)O)(2)] x H(2)O undergoes a sharp dielectric anomaly and a paraelectric-to-ferroelectric phase transition at approximately -23 degrees C with a spontaneous polarization of 1.04 microC cm(-2), being the first molecular metal coordination compound ferroelectrics with a large dielectric response involving a 2 orders of magnitude enhancement and distinct Curie phase transition point. This work has proved an effective way for exploration of new ferroelectrics based on a five-coordinated divalent metal through the combination of crystal engineering and Landau phase transition theory.

Platinum Metal Complexes of Carbaboranylphophines: Potential Anti Cancer Agents

Polyhedral heteroboranes in particular dicarba-closo-dodecaboranes(12) and their organic derivatives have been the subject of intense research for over 40 years due to their unique chemical and physical properties. The initial attraction to dicarba-closo-dodecaboranes(12) In the medicinal chemistry research, was a result of their high boron content and stability to catabolism, which are important criteria for cancer therapy, such as BNCT (boron neutron capture therapy) agents. The coordination compounds of the platinum group metals have also received large interest for their potential application as chemotherapeutic agents, since cis-diamminedichloroplatinum(II), cisplatin, has been reported to have capability as tumor inhibitor. Hence, applications can be envisioned for related cis platinum complexes. Complex of cis-rac-[PtCl2{1,2-(PRCl)2C2B10H10}] (R=Ph, tBu, NEt2, NPh2) have been synthesized by employing known carbaborane based phosphine ligands of clorophoshino-closo-dodecaborane , with complex of cis-[PtCl2(COD)] (COD = 1,5-cyclooctadiene) in an N2-atmosphere. The obtained complexes possess expected structure configuration, namely cis-rac. The characterization of the complex has been carried out using 1H, 31P, 13C and 11B-NMR (Nuclear Magnetic Resonance), X-ray of single crystals, elemental analysis, IR (infra red) and mass spectroscopy (MS). The 31P{1H} NMR spectra of all the platinum complexes distinctly show the typical platinum satellites which are attributed to 31P-195Pt-coupling, in which the 31P{1H} NMR spectrum exhibits three lines with an intensity ratio of ca.1:4:1. The structure of the platinum complexes consists of a slightly distorted square-planar coordination sphere, in which the platinum atom is bonded to two chlorides and two phosphorus atoms of the chelating carbaboranylphosphine. Thus the platinum atoms exhibit the coordination number four, which is preferred in platinum(II) complexes.Keywords: Platinum complexes, phosphine ligand, carbaborane

Color switching in nanocomposites comprising inorganic nanoparticles dispersed in a polymer matrix

Although nanoparticles have found application as dyes already for millennia and experiments in the area of color transformations with nanoparticles have been realized for more than 100 years, color switching in polymer nanocomposites by means of inorganic particles has been explored more systematically only in the last 10–15 years (yet there are still relatively few systems characterized so far). Particles employed for this purpose have been, e.g., metals (gold, silver), transition metal oxides (polyoxometalates, titanium oxides) or coordination compounds (Prussian Blue, Ruthenium Purple). Importantly, the color of nanoparticles, in particular of metal particles, can depend on their sizes and shapes, and also on the interparticle distances. Changing these characteristics in nanocomposites therefore results in optical switching, induced e.g. by heat (thermochromic nanocomposites) or exposure to solvents. Also, an anisotropic arrangement of nanoparticles in the polymer matrix can offer the possibility for color transformations with polarized light (dichroism). Color alterations can further be generated by chemical reactions in nanoparticles, in particular redox reactions initiated by application of a voltage or by light (electrochromic or photochromic nanocomposites, respectively). Notably, the color changes can occur immediately or take hours or days, and the corresponding color variations can be reversible or irreversible, depending on the system. While basically color switching in nanocomposites is suited for many applications, a challenge for their production is the transfer from the laboratory to the industrial scale.

A systematic review of the application of vibrational spectroscopy to the determination of the structures of NO adsorbed on single-crystal metal surfaces

Recently derived vibrational spectroscopic data from NO ligands in metal coordination or cluster compounds, corrected to 'neutral coligand' status, are used to help identify the structures of related surface species from NO chemisorbed on metal single-crystal surfaces at low coverage. The derived conclusions form the basis for a systematic review of the structural information derivable from the extensive vibrational spectroscopic literature in this area, considered in relation to information from other physical methods and density-function theoretical calculations. A high degree of agreement is found for the approximate wavenumber ranges associated with surface species as follows, (cm(-1)) nu(NO) on-top 1700-1860;. 2-fold bridged 1560-1700; 3-fold hollow 1460-1620; 4-fold hollow ca.900: nu(MN) on-top 400-510; 2-fold bridged ca.400; 3-fold hollow 300-405. Within these ranges wavenumber values increase with coverage.

Coordination chemistry of platinum and palladium in the solid-state: Synthesis of imidazole and pyrazole complexes

Solid-state reactions of palladium(II) and platinum(II) chloride complexes with imidazole (Him) and pyrazole (Hpz) or their hydrochloride salts are shown to produce metal complex salts and coordination compounds. Thus, K(2)[MCl(4)] or MCl(2) can be ground with imidazolium chloride ([H(2)im]Cl) to produce the salts [H(2)im](2)[MCl(4)] (M = Pd, 1; Pt, 5), which can then be dehydrochlorinated in the solid state to produce the coordination compounds trans-[PdCl(2)(Him)(2)] 3 or cis-[PtCl(2)(Him)(2)] 6. The complex cis-[PdCl(2)(Him)(2)] 2 is produced when Pd(OAc)(2) is ground with [H(2)im]Cl. Reaction of platinum chloride reagents with imidazole (Him) also produces cis-[PtCl(2)(Him)(2)] 6, but reaction of imidazole with analogous palladium chloride reagents first produces [Pd(Him)(4)]Cl(2) 4 which then slowly converts to trans-[PdCl(2)(Him)(2)] 3. Grinding pyrazolium chloride with K(2)[MCl(4)] produces [H(2)pz](2)[MCl(4)] (M = Pd, 7; Pt, 10), which may also be dehydrochlorinated in the solid state to produce the coordination compounds trans-[PdCl(2)(Hpz)(2)] 8 or cis-[PtCl(2)(Hpz)(2)] 11. Grinding K(2)[PdCl(4)] or PdCl(2) with pyrazole gives [Pd(Hpz)(4)]Cl(2) 9, which is then slowly converted into trans-[PdCl(2)(Hpz)(2)] 8. Grinding PtCl(2) with Hpz generates [Pt(Hpz)(4)]Cl(2) 12, but using K(2)PtCl(4) as the metal source does not generate the same product. The single-crystal structures of 8, a new polymorph of 11 and [H(2)pz](2)[PtCl(6)].2H(2)O (isolated as a decomposition product) are reported for the first time, and the structures of 5 and 10 have been solved ab ibitio from XRPD data.

Structurally Diverse Metal Coordination Compounds, Bearing Imidodiphosphinate and Diphosphinoamine Ligands, as Potential Inhibitors of the Platelet Activating Factor

Metal complexes bearing dichalcogenated imidodiphosphinate [R2P(E)NP(E)R2′]− ligands (E = O, S, Se, Te), which act as (E,E) chelates, exhibit a remarkable variety of three-dimensional structures. A series of such complexes, namely, square-planar [Cu{(OPPh2)(OPPh2)N-O, O}2], tetrahedral [Zn{(EPPh2)(EPPh2)N-E,E}2], E = O, S, and octahedral [Ga{(OPPh2)(OPPh2)N-O,O}3], were tested as potential inhibitors of either the platelet activating factor (PAF)- or thrombin-induced aggregation in both washed rabbit platelets and rabbit platelet rich plasma. For comparison, square-planar [Ni{(Ph2P)2N-S-CHMePh-P, P}X2], X = Cl, Br, the corresponding metal salts of all complexes and the (OPPh2)(OPPh2)NH ligand were also investigated. Ga(O,O)3 showed the highest anti-PAF activity but did not inhibit the thrombin-related pathway, whereas Zn(S,S)2, with also a significant PAF inhibitory effect, exhibited the highest thrombin-related inhibition. Zn(O,O)2 and Cu(O,O)2 inhibited moderately both PAF and thrombin, being more effective towards PAF. This work shows that the PAF-inhibitory action depends on the structure of the complexes studied, with the bulkier Ga(O,O)3 being the most efficient and selective inhibitor.

Blue Luminescent Zn(II) and Hg(II) Complexes with 2-[4-(Dimethylamino)styryl]pyridine; Structural and Luminescent Properties

Luminescent organic and metal coordination compounds have attracted considerable attention for their potential applications in electroluminescent displays. Among coordination compounds, chelate d metal complexes are of great interest due to their high thermal stability and low cost as well as their good photoluminescent and electroluminescent properties. For example, Zn(II) complexes with nitrogen and oxygen donor atoms exhibit blue and white emissions. Meanwhile, less luminescent Hg(II) complexes have been reported. Recently some coordination polymeric Hg(II) complexes have shown blue fluorescence originating from intraligand charge transfer (ILCT) transitions. Herein, two novel d metal (M = Znand Hg) complexes with 2-[4-(dimethylamino)styryl] pyridine (dmasp) were prepared and their structural and luminescent properties were investigated. The dmasp ligand was of interest as it had an electron push-pull system, thereby stabilizing the π* levels and, in them, ILCT transitions could arise readily through a conjugated π system, which is also important to ILCT photoluminescent materials as well as the second-order nonlinear optical (NLO) materials.

Enhanced cell permeability of kojic acid–phenylalanine amide with metal complex

Kojic acid–phenylalanine amide (KA–F–NH 2), which showed an excellent tyrosinase inhibitory activity, did not inhibit melanogenesis in melanocyte due to its low cell permeability. To enhance its cell permeability by increasing lipophilicity, we prepared metal coordination compounds of KA–F–NH 2 and characterized them by FT-IR and ICP analysis. The metal complex of KA–F–NH 2 inhibited mushroom tyrosinase activity as much as KA–F–NH 2 and reduced melanin contents in melanocyte efficiently.

Performance of Kinetic Energy Functionals for Interaction Energies in a Subsystem Formulation of Density Functional Theory.

We have tested the performance of a large set of kinetic energy density functionals of the local density approximation (LDA), the gradient expansion approximation (GEA), and the generalized gradient approximation (GGA) for the calculation of interaction energies within a subsystem approach to density functional theory. Our results have been obtained with a new implementation of interaction energies for frozen-density embedding into the Amsterdam Density Functional program. We present data for a representative sample of 39 intermolecular complexes and 15 transition metal coordination compounds with interaction energies spanning the range from -1 to -783 kcal/mol. This is the first time that kinetic energy functionals have been tested for such strong interaction energies as the ligand-metal bonds in the investigated coordination compounds. We confirm earlier work that GGA functionals offer an improvement over the LDA and are particularly well suited for weak interactions like hydrogen bonds. We do, however, not find a particular reason to prefer any of the GGA functionals over another. Functionals derived from the GEA in general perform worse for all of the weaker interactions and cannot be recommended. An unexpectedly good performance is found for the coordination compounds, in particular with the GEA-derived functionals. However, the presently available kinetic energy functionals cannot be applied in cases in which a density redistribution between the subsystems leads to strongly overlapping subsystem electron densities.

A ruthenium(II) polypyridyl complex for direct imaging of DNA structure in living cells

In the search for new biological imaging agents, metal coordination compounds able to emit from triplet metal-to-ligand charge transfer (MLCT) states offer many advantages as luminescent probes of DNA structure. However, poor cellular uptake restricts their use in live cells. Here, we present a dinuclear ruthenium(II) polypyridyl system that works as a multifunctional biological imaging agent staining the DNA of eukaryotic and prokaryotic cells for both luminescence and transition electron microscopy. This MLCT 'light switch' complex directly images nuclear DNA of living cells without requiring prior membrane permeabilization. Furthermore, inhibition and transmission electron microscopy studies show this to be via a non-endocytotic, but temperature-dependent, mechanism of cellular uptake in MCF-7 cells, and confocal microscopy reveals multiple emission peaks that function as markers for cellular DNA structure.

Assessment of the percutaneous penetration of cisplatin: The effect of monoolein and the drug skin penetration pathway

It was intended to examine the in vitro penetration of cisplatin (CIS) through porcine skin in the presence of different concentrations of monoolein (MO) as well as to verify the main barrier for CIS skin penetration. In vitro skin penetration of CIS was studied from propylene glycol (PG) solutions containing 0%, 5%, 10%, and 20% of MO using Franz-type diffusion cell and porcine ear skin. Pretreatment experiments with MO and experiments with skin without stratum corneum (SC) were also carried out. Skin penetration studies of CIS showed that the presence of MO doubled the drug permeation through the intact skin. However, permeation studies through the skin without SC caused only a small enhancement of CIS permeation compared to intact skin. Moreover, pretreatment of skin with MO formulations did not show any significant increase in the flux of the drug. In conclusion, MO did not act as a real penetration enhancer for CIS, but it increased the drug partition to the receptor solution improving CIS transdermal permeation. The absence of improvement in drug permeation by MO pretreatment and by the removal of SC indicates that the SC is not the main barrier for the permeation of the metal coordination compound.

Molecular self-assembly and patterning induced by sound waves. The case of gelation

Recent findings evidence that cavitational and mechanical effects of ultrasound waves trigger molecular assembly and pattern formation, exemplified by organogels and ordered structures. Although sonication-assisted aggregation has become a well-established protocol, the science behind it is often overlooked. In this tutorial review various aspects of ultrasound-driven reactions are introduced, highlighting organic and metal coordination compounds, as well as recent applications focused on polymer structures. Given the importance of supramolecular assemblies, especially hydrogels, as biomaterials and vehicles for drug transport and delivery, sound waves thus provide a facile entry to new forms of soft matter and functionalized materials.

Isotope Effect on SHG Response and Ferroelectric Properties of a Homochiral Zinc Coordination Compound Containing Tetrazole Ligand

Hydrothermal treatment of a solution of water or deuterium oxide containing N-4-cyanobenzylcinchonidine bromide (CBCBr), NaN3, and Zn(NO3)2·6H2O at 105 °C gave the respective in situ [2 + 3] cycloaddition products (TBC-N4)2Zn(N3)4(X2O) (1, X = H; 2, X = D; CBC-N4 = N-4-tetrazoylbenzylcinchonidine). A study of the SHG, ferroelectric, and permittivity properties of these novel metal-coordination compounds (MCCs) revealed huge deuterated effects (DEF) on SHG (5-fold increase), ferroelectric activity (31% increase), and dielectric behavior (up to 830% increase) upon deuterium substitution from 1 to 2. As expected, the dielectric constants in both dehydrated 1 and dedeuterated 2 are comparable and the DEF is observed to disappear with increasing temperature.

Coordination Compounds of Several Transition Metals with Phenyl-2-pyridyl-ketone

Cobalt (II), nickel (II), copper (II), cadmium (II), and mercury(II) complexes with phenyl-2-pyridyl-ketone as ligand were synthesized at room temperature in ethanolic solution. The donor atoms and the possible geometry of the complexes were determined by means of elemental analysis, molar conductivities, IR, electronic, and EPR spectroscopies, magnetic measurements, and thermogravimmetric analysis.

Influence of specific interactions on the sorption characteristics of porous complexes of 3d metals with derivatives of 4,4′-diazophenyl

Coordination compounds of 3d metals with ligands — azoderivatives of benzidine and 2-hydroxybenzoic acids or 8-hydroxyquinoline — are shown to be characterized by a porous structure capable of absorbing substances of various types. The type of adsorbate is considerably influenced by the specific absorption volume of the complex.

Isostructurality in trivalent metal tris(benzoylacetonates)

Isostructurality is a similarity of the spatial arrangement of molecules off different compounds in their crystal structures. A prerequisite for isostructurality of two compounds is isometry of their molecules. This is best achieved for molecules which differ only in one or few core atoms, while the surface of the molecule remains mostly unchanged [1]. A very good example of such systems are tris(diketonate) coordination compounds of trivalent metals. This was noticed as early as 1926 when has been noted that the crystal structures of trivalent metal pentane-2, 4-dionato complexes of various metals appear to be grouped in several isomorphous series [2]. If the metal atom is coordinated by asymmetrical diketonate, two different isomers (facial and meridial) are possible. Our work concentrated on compounds where trivalent metals are coordinated by 1-phenylbutane-1, 3-dionato ligands which were studied by single crystal X-ray diffraction and thermal analysis. The meridial complexes of iron(III), manganese(III), chromium(III) were already reported to be isomorphous based on their powder diffraction patterns [3]. We have shown that thay crystallize in the monoclinic system, space group P21/c. The only facial isomers which could be isolated where those of chromium(III) and cobalt(III) complexes. They were both found to crystallize in two pseudopolymorphic modifications. Pure compounds crystallize in the space group P– 1 with two molecules in the asymmetric unit. The crystal structures of the chromium and cobalt compounds are almost identical. Under same crystallization conditions, both compounds can also crystallize as hydrates. The hydrates crystallize in the space group R– 3 with 12 molecules per unit cell. The two symmetrically independent molecules in the structure differ in the mode of hydratation. As is the case with the triclinic modifications, the trigonal modifications of both chromium and cobalt compounds are almost perfectly isostructural. [1] A. Kalman, L. Parkanyi, G. Argay, Acta Cryst. (1993) B49, 1039. [2] W. T. Astbury, Proc. Roy. Soc. (1926) 28, 313. [3] R. C Fay, T. S. Piper, J. Am. Chem. Soc. (1962) 84, 2303.

Naphthyridines as building blocks: the helix structure of 2-N-acetylamino-7-methyl-1,8-naphthyridine

24 European Crystallographic Meeting, ECM24, Marrakech, 2007 Page s154 Acta Cryst. (2007). A63, s154 systems are tris(diketonate) coordination compounds of trivalent metals. This was noticed as early as 1926 when has been noted that the crystal structures of trivalent metal pentane-2,4-dionato complexes of various metals appear to be grouped in several isomorphous series [2]. If the metal atom is coordinated by asymmetrical diketonate, two different isomers (facial and meridial) are possible. Our work concentrated on compounds where trivalent metals are coordinated by 1-phenylbutane-1,3-dionato ligands which were studied by single crystal X-ray diffraction and thermal analysis. The meridial complexes of iron(III), manganese(III), chromium(III) were already reported to be isomorphous based on their powder diffraction patterns [3]. We have shown that thay crystallize in the monoclinic system, space group P21/c. The only facial isomers which could be isolated where those of chromium(III) and cobalt(III) complexes. They were both found to crystallize in two pseudopolymorphic modifications. Pure compounds crystallize in the space group P–1 with two molecules in the asymmetric unit. The crystal structures of the chromium and cobalt compounds are almost identical. Under same crystallization conditions, both compounds can also crystallize as hydrates. The hydrates crystallize in the space group R–3 with 12 molecules per unit cell. The two symmetrically independent molecules in the structure differ in the mode of hydratation. As is the case with the triclinic modifications, the trigonal modifications of both chromium and cobalt compounds are almost perfectly isostructural

Deuteration Effect of Ferroelectricity and Permittivity on Homochiral Zinc Coordination Compound

Hydrothermal [2+3] cycloaddition reactions of N-4‘-caynobenzylcinchonidine bromide (CBCBr) with NaN3 in the presence of ZnBr2 offer a novel Zn dimer (CBC−N4)2ZnBr2(N3)2(X2O), X = H for 1 and D for 2) in which the reactant Br- and N3- take part in the coordination to Zn. The measurements of ferroelectricity and permittivity of 1 and 2 show that there exists a large deuterated effect both in ferroelectric behavior (40% increase) and in dielectric constant (2.75 times increase), which is unprecedented in metal coordination compounds.