Trigonal Planar Research Articles

Synthesis and Reactions of 3d Metal Complexes with the Bulky Alkoxide Ligand [OC(t)Bu2Ph

Treatment of NiCl2(dme) and NiBr2(dme) (dme = dimethoxyethane) with 2 equiv of LiOR (OR = OC(t)Bu2Ph) forms the distorted trigonal planar complexes [NiLiX(OR)2(THF)2] (THF = tetrahydrofuran) 5 (X = Cl) and 6 (X = Br). The reaction of CuX2 (X = Cl, Br) with 2 equiv of LiOR affords the Cu(I) product Cu4(OR)4 (7). The same product can be obtained using the Cu(I) starting material CuCl. NMR studies indicated that the reduction of Cu(II) to Cu(I) is accompanied by the oxidation of the alkoxide RO(-) to form the alkoxy radical RO(•), which subsequently forms tert-butyl phenyl ketone by β-scission. Treatment of compounds 1-4 ([M2Li2Cl2(OR)4], M = Cr-Co) with thallium hexafluorophosphate allowed the isolation of the distorted tetrahedral complexes of the form M(OR)2(THF)2 for M = Mn (8), Fe (9), and Co (10). Cyclic voltammetry performed on compounds 8-10 demonstrated irreversible oxidations for all complexes, with the iron complex 9 being the most reducing. Complex 9 shows a reactivity toward PhIO and Ph3SbS to form the corresponding dinuclear iron(III) complexes Fe2(O)(OR)4(THF)2 (11) and Fe2(S)(OR)4(THF)2 (12), respectively. X-ray structural studies were performed, showing that the Fe-O-Fe angle for complex 11 is 176.4(1)° and that the Fe-S-Fe angle for complex 12 is 164.83(3)°.

Crystal structure of di-μ-iodido-bis-{[1,3-bis-(2,6-diiso-propyl-phen-yl)imidazol-2-yl-idene]lithium}.

In the title binuclear complex, [Li2(C27H36N2)2I2], the unique LiI cation is coordinated by two iodide anions and one yl­idene C atom from a 1,3-bis­(2,6-diiso­propyl­phen­yl)imidazol-2-yl­idene ligand in a distorted trigonal–planar geometry. The two symmetry-related iodide anions bridge two LiI cations, forming an inversion dimer in which the Li2I2 plane is nearly perpendicular to the imidazol-2-yl­idene ring, with a dihedral angle of 85.5 (3)°. No hydrogen bonding is observed in the crystal.

Bis-hydrocarbyl Platinum(II) Ambiphilic Ligand Complexes: Alkyl–Aryl Exchange between Platinum and Boron

Reaction of TXPB (2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene) with [PtMe2(COD)] (COD = 1,5-cyclooctadiene) yielded [PtMePh(TXPB′)] (1; TXPB′ = 2,7-di-tert-butyl-5-methylphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene), presumably via undetected [PtMe2(TXPB)]. The ambiphilic ligand in 1 is κ2PS-coordinated, and the trigonal plane of the borane is oriented approximately parallel to the square plane at platinum. In solution, 1 is in equilibrium with zwitterionic [PtMe(TXPB-Me)] (1′), in which the Pt-phenyl group in 1 has been abstracted by the borane; the ratio of 1 to 1′ is approximately 90:10 at room temperature and 50:50 at 183 K. The presence of 1′ in solution suggests that the pathway for phenyl–methyl exchange between platinum and boron involves a zwitterionic platinum(II) intermediate, rather than a platinum(IV) boryl complex resulting from B–C bond oxidative addition. Heating compound 1 provided an approximate 14:86 mixture of 1 and [PtPh2(TXPB″)] (2; TXPB...

Noncentrosymmetric rare-earth copper gallium chalcogenides RE3CuGaCh7 (RE=La–Nd; Ch=S, Se): An unexpected combination

The quaternary rare-earth chalcogenides RE3CuGaS7 and RE3CuGaSe7 (RE=La–Nd) have been prepared by reactions of the elements at 1050°C and 900°C, respectively. They crystallize in the noncentrosymmetric La3CuSiS7-type structure (hexagonal, space group P63, Z=2) in which the a-parameter is largely controlled by the RE component (a=10.0–10.3Å for the sulfides and 10.3–10.6Å for the selenides) whereas the c-parameter is essentially fixed by the choice of Ga and chalcogen atoms within tetrahedral units (c=6.1Å for the sulfides and 6.4Å for the selenides). They extend the series RE3MGaCh7, previously known for divalent metal atoms (M=Mn–Ni), differing in that the Cu atoms in RE3CuGaCh7 occupy trigonal planar sites instead of octahedral sites. Among quaternary chalcogenides RE3MM′Ch7, the combination of monovalent (M=Cu) and trivalent (M′=Ga) metals is unusual because it appears to violate the condition of charge balance satisfied by most La3CuSiS7-type compounds. The possibility of divalent Cu atoms was ruled out by bond valence sum analysis, magnetic measurements, and X-ray photoelectron spectroscopy. The electron deficiency in RE3CuGaCh7 is accommodated through S-based holes at the top of the valence band, as shown by band structure calculations on La3CuGaS7. An optical band gap of about 2.0eV was found for La3CuGaSe7.

Synthesis of two new silver(I) complexes with 3-bromoquinoline: Molecular structure, spectroscopic characterizations and DFT studies

Two new Ag+ complexes with 3-bromoquinoline (3BrQ) have been synthesized and characterized using elemental analysis, FTIR, NMR and mass spectra. The studied complexes have the formula [Ag(3BrQ)(OAC)]; 1 and [Ag(3BrQ)3(TCA)]; 2 where OAC and TCA are acetate and trichloroacetate, respectively. Based on the DFT calculations, 1 and 2 showed distorted trigonal planar and distorted tetrahedral coordination geometry. The electronic properties such as dipole moment (μ), polarizability (α0), HOMO and LUMO energies are calculated using the same level of theory. These electronic parameters were used to predict the nonlinear optical properties of the studied compounds. The studied silver complexes were predicted to be better nonlinear optical materials than urea. The electronic spectra of these complexes are calculated using the TD–DFT calculations. The infrared vibrational spectra were assigned based on the potential energy distribution (PED) analysis. The calculated 1H NMR chemical shift values using GIAO approach showed good agreement with the experimental data. The intramolecular charge transfer interactions of the title molecules were studied by natural bond orbital (NBO) analysis.

Synthesis and Structure of a Trigonal Planar Complex with Pyrazole Ligands, [Cu(3,5-Ph2PzH)3][Cl

The crystal structure of a trigonal planar copper(I) complex, [Cu-(3,5-Ph2PzH)3][Cl], is reported. In the title compound, one nitrogen atom from each pyrazole ligand is coordinated to the copper(I) ion and each N–H of the pyrazoles forms a hydrogen-bond with the chloride resulting in a trigonal planar geometry about the copper(I) ion. The complex crystallizes in the trigonal space group R $$\overline 3$$ with a = b = 13.031(1) A, c = 37.3187(9) A, α = β = 90o, γ = 120o , V = 5464.5(2) A3, Z = 6. A trigonal planar copper(I) complex with three pyrazole ligands is reported in which the hydrogens of the bound pyrazole ligands are hydrogen bonded with the chloride counter ion.

Crystalline TQPP as p-type semiconductor: X-ray crystallographic investigation, OTFT device, and computational analysis of transport properties

Two p-type semiconducting azapyrenoacene materials, quinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine (TQPP) and 6,7,15,16-tetramethylquinoxalino[2′,3′:9,10]phenanthro[4,5-abc]phenazine (TQPP-[CH3]4), were characterized and were found to display high thermal stability and planar molecular geometry as revealed by single-crystal X-ray analysis. In bottom-gate p-channel organic thin-film transistors, field-effect mobilities of 2.5×10−3cm2/Vs and 7.5×10−5cm2/Vs were measured in ambient air for TQPP and TQPP-[CH3]4, respectively. Computational results of reorganization energies and electronic couplings indicate larger inter and intra-columnar couplings for TQPP-[CH3]4 in comparison to TQPP and predict the suitability of both semiconductors for hole as well as electron transporters.

Double-layer structure, sorption and magnetism properties of metal–organic frameworks with trigonal planar ligand

A new double-layer metal–organic framework [Co3(tcpt)2(H2O)2] (1) has been synthesized using trigonal planar ligand 2,4,6-tris(4-carboxyphenoxy)-1,3,5-triazine (H3tcpt) as a bridging ligand and characterized by single-crystal X-ray diffraction, elemental analyses, IR, PXRD and TGA. Structure analysis reveals that compound 1 has a double-layer structure. Gas sorption measurements indicate that compound 1 exhibits selective adsorption capabilities for CO2 over CH4 and N2. Furthermore, the magnetic studies of compound 1 show antiferromagnetic interactions between Co(II) ions.

Crystal structure of catena-poly[[silver(I)-{μ-2,6-bis-[(1H-pyrazol-1-yl)meth-yl]pyridine-κ(3) N (1),N (2):N (2')}] nitrate

In the title complex, {[Ag(C13H13N5)]NO3}n, the AgI atom is coordinated by three N atoms from two bidentate/monodentate pyrazolylpyridyl ligands to form a distorted trigonal–planar geometry [range of angles: 83.34 (6) (chelate ring) to 139.15 (7) °]. The chelate ring has a distorted boat conformation. The dihedral angle between the pyridyl ring and the coordinating pyrazolyl ring is 67.22 (6)°. The non-coordinating pyrazolyl ring is twisted by 62.97 (7)° from the pyridyl ring. In the crystal, the complex cations are arranged in polymeric chains along the c-axis direction, with the nitrate counter-anions situated in between. Weak C—H⋯O hydrogen bonds link the ions into a three-dimensional network.

Synthesis and photophysical properties of GemPhos noble metal complexes

GemPhos, a diphosphine ligand with a rigid paracyclophane scaffold, was used to prepare complexes of the noble metals gold, palladium, and platinum. The reaction of GemPhos with [Au(tht)2][ClO4] (tht = tetrahydrothiophene) surprisingly yielded a mononuclear charge separated gold compound [(GemPhos)Au][ClO4], in which the gold atom exhibits an uncommon trigonal planar coordination geometry. Furthermore, similar palladium [(GemPhos) (PdCl2)] and platinum [(GemPhos)(PtCl2)] complexes were obtained in very good yields by the reaction of GemPhos with [MCl2(COD)] (M = Pd, Pt; COD = 1,5-cyclooctadiene) in hot DMSO. All compounds were fully characterized by analytical and spectroscopic techniques and their solid-state structures were established by single X-ray crystallography. Their photoluminescent properties were measured at low and ambient temperatures, revealing different behavior depending on the metal and coordination mode.

A family of tri- and dimetallic pyridine dicarboxamide cryptates: unusual O,N,O-coordination and facile access to secondary coordination sphere hydrogen bonding interactions.

A series of tri- and dimetallic metal complexes of pyridine dicarboxamide cryptates are reported in which changes to the base and metal source result in diverse structure types. Addition of strong bases, such as KH or KN(SiMe3)2, followed by divalent metal halides allows direct access to trinuclear complexes in which each metal center is coordinated by a dianionic N,N,N-chelate of each arm. These complexes bind a guest K(+) cation within the central cavity in a trigonal planar coordination environment. Minor changes to the solvent and equivalents of base used in the syntheses of the triiron(II) and tricobalt(II) complexes affords two trinuclear clusters with atypical O,N,O-coordination by each pyridine dicarboxamide arm; the amide carbonyl O atoms are oriented toward the interior of the cavity to coordinate to each metal center. Finally, varying the base enables the selective synthesis of dinuclear nickel(II) and copper(II) complexes in which one pyridine dicarboxamide arm remains protonated. These amide protons are at one end of a hydrogen bonding network that extends throughout the internal cavity and terminates at a metal bound hydroxide, carbonate, or bicarbonate donor. In the dinickel complex, the bicarbonate cannot be liberated as CO2 either thermally or upon sparging with N2, which differs from previously reported monometallic complexes. The carbonate or bicarbonate ligands likely arise from sequestration of atmospheric CO2 based on the observed reaction of the di(hydroxonickel) analog.

Crystal structure of [1-(2,6-diiso-propyl-phen-yl)-2,4-bis-(di-methyl-amino)-5-tri-methyl-silyl-1,3,5-tri-aza-penta-dienyl-κ(2) N (1),N (5)](tri-phenyl-phosphane-κP)copper(I).

The title complex, [Cu(C21H38N5Si)(C18H15P)], was obtained from the one-pot reaction between (Dipp)N(Li)SiMe3 (Dipp = 2,6-diiso­propyl­phen­yl), Me2NCN, CuCl and PPh3. The CuI atom has a distorted trigonal–planar coordination sphere. The tri­aza­penta­dienyl ligand acts as a κ2-donor. The N—Cu—N bond angle is 95.88 (14)°. In the tri­aza­penta­dienyl fragment, the C—N bond lengths are in the range 1.328 (5)–1.349 (5) Å, which indicates delocalization of the π-electrons in the NCNCN system.

Ferromagnetic copper(II)–copper(II) interaction in a single chlorido and dicyanamido bridged mixed–valence copper(I/II) 2-D polymer generated by in situ partial reduction of copper(II)

A mixed-valence 2-D Cu(I/II) complex, [{Cu(II)(dmen)(μ-Cl)(μ1,5-dca)}{Cu(I)(μ1,5-dca)}]n (1) (dmen = N,N-dimethylethylenediamine, dca = dicyanamide = [N(CN)2]−), has been synthesized by in situ partial reduction of Cu(II) to Cu(I) using benzoin (2-hydroxy-1,2-di(phenyl)ethanone) as reductant. Complex 1 was characterized by spectroscopic techniques, single crystal X-ray diffraction, and low temperature magnetic measurements. Structural investigation reveals that 1 represents a mixed-valence 2-D coordination polymer formed by parallel 1-D [Cu(II)(dmen)(Cl)Cu(I)(μ1,5-dca)2]n chains running along the b axis, where chloride bridges Cu(II) ions of adjacent polymers through long connections (2.8401(1) Å) to form a 2-D network. The metal centers have two different geometrical environments (distorted square pyramidal and distorted trigonal planar geometries for Cu(II) and Cu(I), respectively). The Cu(II) ions in [Cu(II)(dmen)(μ-Cl)(dca)]n are interconnected through single chloride bridges while within the [Cu(I)(μ1,5-dca)]n units, the dca connects adjacent Cu(I) ions through μ1,5-dca bridges. Magnetic susceptibility measurements reveal weak ferromagnetic interactions (J = +0.3 cm−1) within the chlorido-bridged Cu(II) regular chain present in 1. Simultaneous presence of μ1,5-dca and single chlorido bridges with ferromagnetic coupling is believed to be unique in mixed-valence Cu(I)/Cu(II) complexes.

Homoleptic Trigonal Planar Lanthanide Complexes Stabilized by Superbulky Silylamide Ligands

The lithium silylamides [Li(μ3-NHSiMe2But)]6 (1) and [Li(μ-NHSiPri3)(THF)]2 (2) were reacted with ClSiMe3, ClSiMe2But, or ClSiPri3 to prepare a series of secondary silylamines by salt metathesis reactions. These were deprotonated with KH to afford the group 1 transfer agents [K{μ-N(SiMe2But)(SiMe3)}(C7H8)]2 (3), [{K[μ-N(SiPri3)(SiMe3)]}2]∞ (4), [{K[μ-N(SiMe2But)2]}2(C7H8)]∞ (5), [K{N(SiPri3)(SiMe2But)}]∞ (6), [K{N(SiPri3)2}]∞ (7), and [K{N(SiPri3)2}(THF)3] (8). The synthetic utility of these group 1 transfer agents has been demonstrated by their reactions with [Ln(I)3(THF)4] (Ln = La, Ce) in various stoichiometries to yield heteroleptic [La{N(SiMe2But)(SiMe3)}2(μ-I)]2 (9) and homoleptic [Ln{N(SiMe2But)(SiMe3)}3] (Ln = La 10, Ce 11) and [La{N(SiMe2But)2}3] (12). The very bulky silylamide ligands described herein can impart unusual geometries to their lanthanide complexes. Complexes 10–12 remarkably exhibit approximate planarity in the solid state rather than the more common trigonal pyramidal shapes observ...

X-ray structures versus NMR signals in pentacoordinate [PtX2(η2-CH2[dbnd]CH2)(Me2phen)] (X = Cl, Br, I) complexes

The single crystal X-ray structure of the pentacoordinate complex [PtBr2(η2-CH2CH2)(Me2phen)], Me2phen=2,9-dimethyl-1,10-phenanthroline, is here reported for the first time. Comparison of the complete series of [PtX2(η2-CH2CH2)(Me2phen)] (X=Cl, Br, I) X-ray structures shows a very low variability of the bond lengths and angles, in the trigonal equatorial plane (where η2-olefin and Me2phen are bound), on varying the coordinated axial halogens. In first approximation, this suggests describing as independents and not interacting the two subsystems constituted by the metal bonds with axial (X–Pt–X) and equatorial ligands (Me2phen–Pt–η2-ethene). This means that the electric charge donated to the metal, by the axial ligands, cannot substantially modify the bonds of the metal with the ligands in the trigonal equatorial plane. The 1H, 13C, 15N and 195Pt NMR chemical shifts variations, studied as a function of the ionic radius of the axial halides are here discussed. The NMR data strongly suggest the existence of electric pseudo-ring currents circulating around the Pt–X axes and modulated by the ionic radius of the coordinated halides.

Photoelectron spectroscopy and theoretical studies of anion-π interactions: binding strength and anion specificity.

Proposed in theory and then their existence confirmed, anion-π interactions have been recognized as new and important non-covalent binding forces. Despite extensive theoretical studies, numerous crystal structural identifications, and a plethora of solution phase investigations, anion-π interaction strengths that are free from complications of condensed-phase environments have not been directly measured in the gas phase. Herein we present a joint photoelectron spectroscopic and theoretical study on this subject, in which tetraoxacalix[2]arene[2]triazine 1, an electron-deficient and cavity self-tunable macrocyclic, was used as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states (spherical halides Cl(-), Br(-), I(-), linear thiocyanate SCN(-), trigonal planar nitrate NO3(-), pyramidic iodate IO3(-), and tetrahedral sulfate SO4(2-)). The binding energies of the resultant gaseous 1 : 1 complexes (1·Cl(-), 1·Br(-), 1·I(-), 1·SCN(-), 1·NO3(-), 1·IO3(-) and 1·SO4(2-)) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion-specific effects. The binding strengths of Cl(-), NO3(-), IO3(-) with 1 are found to be strongest among all singly charged anions, amounting to ca. 30 kcal mol(-1), but only about 40% of that between 1 and SO4(2-). Quantum chemical calculations reveal that all the anions reside in the center of the cavity of 1 with an anion-π binding motif in the complexes' optimized structures, where 1 is seen to be able to self-regulate its cavity structure to accommodate anions of different geometries and three-dimensional shapes. Electron density surface and charge distribution analyses further support anion-π binding formation. The calculated binding energies of the anions and 1 nicely reproduce the experimentally estimated electron binding energy increase. This work illustrates that size-selective photoelectron spectroscopy combined with theoretical calculations represents a powerful technique to probe anion-π interactions and has potential to provide quantitative guest-host molecular binding strengths and unravel fundamental insights in specific anion recognitions.

Fluorescent mixed ligand copper(II) complexes of anthracene-appended Schiff bases: studies on DNA binding, nuclease activity and cytotoxicity.

A series of mixed ligand copper(ii) complexes of the type [Cu(L)(phen)(ACN)](ClO4)21-5, where L is a bidentate Schiff base ligand (N(1)-(anthracen-10-ylmethylene)-N(2)-methylethane-1,2-diamine (L1), N(1)-(anthracen-10-ylmethylene)-N(2),N(2)-dimethylethane-1,2-diamine (L2), N(1)-(anthracen-10-yl-methylene)-N(2)-ethylethane-1,2-diamine (L3), N(1)-(anthracen-10-ylmethylene)-N(2),N(2)-diethylethane-1,2-diamine (L4) and N(1)-(anthracen-10-ylmethylene)-N(3)-methylpropane-1,3-diamine (L5)) and phen is 1,10-phenanthroline, have been synthesized and characterized by spectral and analytical methods. The X-ray crystal structure of 5 reveals that the coordination geometry around Cu(ii) is square pyramidal distorted trigonal bipyramidal (τ, 0.76). The corners of the trigonal plane of the geometry are occupied by the N2 nitrogen atom of phen, the N4 nitrogen atom of L5 and the N5 nitrogen of acetonitrile while the N1 nitrogen of phen and the N3 nitrogen of L5 occupy the axial positions with an N1-Cu1-N3 bond angle of 176.0(3)°. All the complexes display a ligand field band (600-705 nm) and three less intense anthracene-based bands (345-395 nm) in solution. The Kb values calculated from absorption spectral titration of the complexes (π→π*, 250-265 nm) with Calf Thymus (CT) DNA vary in the order 5 > 4 > 3 > 2 > 1. The fluorescence intensity of the complexes (520-525 nm) decreases upon incremental addition of CT DNA, which reveals the involvement of phen rather than the appended anthracene ring in partial DNA intercalation with the DNA base stack. The extent of quenching is in agreement with the DNA binding affinities and the relative increase in the viscosity of DNA upon binding to the complexes as well. Thus 5 interacts with DNA more strongly than 4 on account of the stronger involvement in hydrophobic DNA interaction of the anthracenyl moiety, which is facilitated by the propylene ligand backbone with chair conformation. The ability of complexes (100 μM) to cleave DNA (pUC19 DNA) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.1 in the absence of a reducing agent or light varies in the order 5 > 4 > 3 > 2 > 1, which is in conformity with their DNA binding affinities. Interestingly, cytotoxicity studies on the MCF-7 human breast cancer cell line show that the IC50 value of 5 is less than that of cisplatin for the same cell line, revealing that it can act as an effective cytotoxic drug in a time-dependent manner.

Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {Mn(III)3Na2} complex with an ideal trigonal bipyramidal geometry.

The successful organic synthesis of a new dipyrazole/pyridine-dicarbonyl organic molecule, namely pyridine-2,6-diylbis(pyrazine-2-ylmethanone) [(pz)CO(py)CO(pz)], followed by its employment in Mn coordination chemistry has yielded the neutral cluster compound [Mn3Na2O(N3)3(L)3] (1), where L(2-) is the (pz)C(CH2COCH3)(O(-))(py)C(CH2COCH3)(O(-))(pz) dianion. The latter group was formed in situ, presumably by the nucleophilic attack of the carbanion (-)CH2COCH3 to the carbonyl carbon atoms of (pz)CO(py)CO(pz), in the presence of Mn(n+) ions under basic conditions and in solvent Me2CO. Complex 1 possesses an almost ideal trigonal bipyramidal topology, with the two Na(I) ions occupying the apical positions and the three Mn(III) ions residing in the equatorial trigonal plane. The bridging ligation about the metal ions is provided by a μ3-O(2-) ion and six μ-OR(-) groups from the L(2-) ligand, while peripheral ligation is completed by three terminal azido groups and the pyridine N and carbonyl O atoms of L(2-). Magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the paramagnetic Mn(III) centres; the use of an anisotropic, equilateral Mn(III)3 triangle model allowed us to fit the magnetic data and obtain the best-fit parameters: J = -10.8 cm(-1), D = -5.3 cm(-1), and g = 1.99. The combined results demonstrate the rich chemical reactivity of carbonyl groups and the ability of poly-ketone ligands to stabilize cluster compounds with unprecedented structural motifs and interesting architectures.

Group 9 organometallic compounds for therapeutic and bioanalytical applications.

CONSPECTUS: Compared with organic small molecules, metal complexes offer several distinct advantages as therapeutic agents or biomolecular probes. Carbon atoms are typically limited to linear, trigonal planar, or tetrahedral geometries, with a maximum of two enantiomers being formed if four different substituents are attached to a single carbon. In contrast, an octahedral metal center with six different substituents can display up to 30 different stereoisomers. While platinum- and ruthenium-based anticancer agents have attracted significant attention in the realm of inorganic medicinal chemistry over the past few decades, group 9 complexes (i.e., iridium and rhodium) have garnered increased attention in therapeutic and bioanalytical applications due to their adjustable reactivity (from kinetically liable to substitutionally inert), high water solubility, stability to air and moisture, and relative ease of synthesis. In this Account, we describe our efforts in the development of group 9 organometallic compounds of general form [M(C(∧)N)2(N(∧)N)] (where M = Ir, Rh) as therapeutic agents against distinct biomolecular targets and as luminescent probes for the construction of oligonucleotide-based assays for a diverse range of analytes. Earlier studies by researchers had focused on organometallic iridium(III) and rhodium(III) half-sandwich complexes that show promising anticancer activity, although their precise mechanisms of action still remain unknown. More recently, kinetically-inert group 9 complexes have arisen as fascinating alternatives to organic small molecules for the specific targeting of enzyme activity. Research in our laboratory has shown that cyclometalated octahedral rhodium(III) complexes were active against Janus kinase 2 (JAK2) or NEDD8-activating enzyme (NAE) activity, or against NO production leading to antivasculogenic activity in cellulo. At the same time, recent interest in the development of small molecules as modulators of protein-protein interactions has stimulated our research group to investigate whether kinetically-inert metal complexes could also be used to target protein-protein interfaces relevant to the pathogenesis of certain diseases. We have recently discovered that cyclometalated octahedral iridium(III) and rhodium(III) complexes bearing C(∧)N ligands based on 2-phenylpyridine could function as modulators of protein-protein interactions, such as TNF-α, STAT3, and mTOR. One rhodium(III) complex antagonized STAT3 activity in vitro and in vivo and displayed potent antitumor activity in a mouse xenograft model of melanoma. Notably, these studies were among the first to demonstrate the direct inhibition of protein-protein interfaces by kinetically-inert group 9 metal complexes. Additionally, we have discovered that group 9 solvato complexes carrying 2-phenylpyridine coligands could function as inhibitors and probes of β-amyloid fibrillogenesis. Meanwhile, the rich photophysical properties of iridium complexes have made them popular tools for the design of luminescent labels and probes. Luminescent iridium(III) complexes benefit from a high quantum yield, responsive emissive properties, long-lived phosphorescence lifetimes, and large Stokes shift values. Over the past few years, our group has developed a number of kinetically-inert, organometallic iridium(III) complexes bearing various C(∧)N and N(∧)N ligands that are selective for G-quadruplex DNA, which is a DNA secondary structure formed from planar stacks of guanine tetrads stabilized by Hoogsteen hydrogen bonding. These complexes were then employed to develop G-quadruplex-based, label-free luminescence switch-on assays for nucleic acids, enzyme activity, small molecules, and metal ions.

Crystal structure of poly[(μ3-thio-cyanato-κ(3) N:S:S)(tri-methyl-phosphine sulfide-κS)copper(I)

In the title compound, [Cu(NCS)(C3H9PS)] n , the thio-cyanate ions bind the Cu(I) atoms covalently, forming infinite -Cu-SCN-Cu- chains parallel to the a axis. Each Cu(I) atom is also coordinated to a tri-methyl-phosphine sulfide group via a Cu-S bond. Two crystallographically independent chains propagate in opposite directions, and are held together in a ribbon arrangement by long bonds between Cu(I) atoms in the first chain and thio-cyanate S atoms in the second, with Cu-S = 2.621 (1) Å. The geometry around the Cu(I) atoms in the first chain is distorted tetra-hedral, with angles involving the long Cu-S bond much less than ideal, and the S-Cu-N angle between the phosphine sulfide S atom and the thio-cyanate N atom opening out to 133.19 (9)°. Each Cu(I) atom in the second chain appears to be disordered between two positions 0.524 (4) Å apart, with occupancy factors of 0.647 (6) and 0.353 (6). The Cu(I) atom in the major site is in a distorted trigonal-planar configuration, with the S-Cu-N angle between the phosphine sulfide and the thio-cyanate N atom again opened out, to 137.01 (15)°. The Cu(I) atom in the minor site, however, forms in addition a long bond [Cu-S = 2.702 (5) Å] to the phosphine sulfide of the first chain, not the thio-cyanate S atom, to provide a further link between the chains.