Synthesis, characterization, crystal structures, and photophysical properties of a series of room-temperature phosphorescent copper(I) complexes with oxadiazole-derived diimine ligand

In this paper, we report four phosphorescent Cu(I) complexes of [Cu(OP)(PPh₃)₂]BF₄, [Cu(Me-OP)(PPh₃)₂]BF₄, [Cu(OP)(POP)]BF₄, and [Cu(Me-OP)(POP)]BF₄ with oxadiazole-derived diimine ligands, where OP = 2-(5-phenyl-[1,3,4]oxadiazol-2-yl)-pyridine, Me-OP = 2-(5-p-tolyl-[1,3,4]oxadiazol-2-yl)-pyridine, POP = bis(2-(diphenylphosphanyl)phenyl) ether, and PPh₃ = triphenylphosphane, including their synthesis, crystal structures, photophysical properties, and electronic nature. The Cu(I) center has a distorted tetrahedral geometry within the Cu(I) complexes. Theoretical calculation reveals that all emissions originate from triplet metal-to-ligand-charge-transfer excited state. It is found that the inter-molecular sandwich structure triggered by inter- and intra-molecular pi-stacking within solid state Cu(I) complexes is highly effective on restricting the geometric relaxation that occurs in excited states, and thus greatly enhances the photoluminescence (PL) performances, including PL quantum yield improvement, PL decay lifetime increase, and emission blue shift.     

Syntheses and structural characterizations of novel mono- and dinuclear iridium hydrido complexes with polydentate nitrogen donor ligands

New five mono- and dinuclear Ir hydrido complexes with polydentate nitrogen ligands, [Ir(H)₂(PPh₃)₂(tptz)]PF₆ (1), [Ir₂(H)₄(PPh₃)₄(tptz)](PF₆)₂ · 2H₂O (2 · 2H₂O), [Ir(H)₂(PPh₃)₂(tppz)]BF₄ (3), [Ir₂(H)₄(PPh₃)₄(tppz)](BF₄)₂ (4) and [Ir₂(H)₄(PPh₃)₄(bted)](BF₄)₂ · 6CHCl₃ (5 · 6CHCl₃), were systematically prepared by the reactions of the precursor Ir hydrido complex [Ir(H)₂(PPh₃)₂(Me₂CO)₂]X (X=PF₆ and BF₄) with 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 1,4-bis(2,2^′:6^′,2″-terpyridine-4^′-yl)benzene (bted), and their structures and properties were characterized in the solid state and in solution. Each of the Ir hydrido complexes with polydentate nitrogen ligands crystallographically described a unique coordination mode. Their ¹H NMR spectra demonstrated unusual ¹H NMR chemical shifts of pyridyl rings that are likely induced by the ring current effect of neighboring ligands.     

Synthesis, structural and spectroscopic characterization of mono- and binuclear copper(I) complexes with substituted diimine and phosphine ligands

The reaction of [Cu(CH₃CN)₄]BF₄, 6-(4-methoxyl)phenyl-2,2′-bipyridine (designated as MeO-CNN), and/or tricyclohexylphosphine (PCy₃) and diimine ligands derived from 4,4′-bipyridine gave four mono- and binuclear copper(I) complexes, [Cu(MeO-CNN)₂]BF₄ (1), [Cu₂(MeO-CNN)₂(PCy₃)₂(4,4′-bipy)](BF₄)₂ · 1.5CH₂Cl₂ (2) (bipy = bipyridine), [Cu₂(MeO-CNN)₂(PCy₃)₂(bpete)](BF₄)₂ · 4CH₂Cl₂ (3) (bpete = trans-1,2-bis(4-pyridyl)ethene) and [Cu₂(MeO-CNN)₂(PCy₃)₂(4,4′-azpy)] (BF₄)₂ · 1.5CH₂Cl₂ (4) (azpy = azobispyridine). Crystallographic studies of complexes 1-4 show that each copper(I) center adopts a pseudo-tetrahedral coordination geometry. Complexes 2-4 consists of -Cu(MeO-CNN)(PCy₃) units which are linked through 4,4′-bipy, bpete and 4,4′-azpy, respectively. The UV-Vis spectra of these four complexes all exhibit intense high-energy absorptions at λ_max < 340 nm and broad visible bands in a range of 430-550 nm, ascribed to intraligand (IL π → π^∗) transitions and metal-to-ligand charge-transfer (MLCT) transitions, respectively. The density functional theory calculation was used to interpret the absorption spectrum of 1, which further supports the assignment of MLCT character. The binuclear complexes 2 and 3 both display red solid-state emissions centred at 620 and 660 nm from metal-to-ligand charge-transfer excited state, respectively. Interestingly, the electron paramagnetic resonance (EPR) spectral measurements confirm copper(I) complexes oxidized to corresponding copper(II)-halide product upon excitation at 355 nm in dichloromethane solution.     

Synthesis and characterization of ruthenium and osmium complexes of heterocyclic bidentate ligands (N, X), X = S, Se

The reaction of [RuCl₂(PPh₃)₃] and [OsBr₂(PPh₃)₃] precursors with a series of heterocyclic bidentate (N, X) ligands, X = S, Se, gave complexes [M(R-pyS)₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF₃, 3-Me₃Si); [M(R-pymS)₂(PPh₃)₂], (R = 4-CF₃, 4,6-MeCF₃) and [M(R-pySe)₂(PPh₃)₂], (R = H, 3-CF₃, 5-CF₃), where M is Ru or Os, pyS and pymS the anions of pyridine-2-thione and pyrimidine-2-thione, respectively, and pySe is the anion produced by the reductive cleavage of the Se-Se bond in the dipyridyl-2,2′-diselenide. All of the compounds obtained were characterized by microanalysis, IR, FAB, NMR spectroscopy and by cyclic voltammetry. Compounds [Ru(3-CF₃-pyS)₂(PPh₃)₂] · 2(CH₂Cl₂) (2), [Ru(3-Me₃Si-pyS)₂(PPh₃)₂] (4), [Ru(4-CF₃-pymS)₂(PPh₃)₂] (5), [Ru(3-CF₃-pySe)₂(PPh₃)₂] · 2(CH₂Cl₂) (8), [Os(3-CF₃-pyS)₂(PPh₃)₂] · (CHCl₃) (11), [Os(3-Me₃Si-pyS)₂(PPh₃)₂] (13), [Os(3-CF₃-pySe)₂(PPh₃)₂] · 2(CH₂Cl₂) (17), [Os(5-CF₃-pySe)₂(PPh₃)₂] · 2(H₂O) (18) and [OsCl₂(4,6-MeCF₃-pymS)(PPh₃)₂] (19) were also characterized by X-ray diffraction. In all cases, the metal is in a distorted octahedral environment with the heterocyclic ligand acting as a bidentate (N, S) chelate system.     

Syntheses, structures, and properties of Co(III) complexes derived from polypyridine ligands containing one carboxamido nitrogen donor

Four cobalt(III) complexes containing the polypyridine pentadentate ligands N,N-bis(2-pyridylmethyl)amine-N′-ethyl-2-pyridine-2-carboxamide (PaPy₃H), N,N-bis(2-pyridylmethyl)amine-N′-[1-(2-pyridylethyl)acetamide (MePcPy₃H), and N,N-bis(2-pyridylmethyl)amine-N′-(2-pyridylmethyl)acetamide (PcPy₃H), have been synthesized. All three ligands bind the Co(III) center in the same fashion with the exception of loss of conjugation between the carboxamide moiety and the pyridine ring in the latter two. The structures of [(PaPy₃)Co(OH)][(PaPy₃)Co(H₂O)](ClO₄)₃ · 3H₂O (1), [(PaPy₃)Co(NO₂)](ClO₄) · 2MeCN (2), [(MePcPy₃)Co(MeCN)](ClO₄)₂ · 0.5MeCN (3), and [(PcPy₃)Co(Cl)](ClO₄) · 2MeCN (4) have been determined. These ligands with strong-field carboxamido N donor stabilize the +3 oxidation state of the Co center as demonstrated by the facile oxidation of the corresponding Co(II) complexes (prepared in situ) by H₂O₂, [Fe(Cp)₂](BF₄), or nitric oxide (NO). The Co-N_amido bond distances of 1-4 lie in the narrow range of 1.853-1.898 Å. ¹H NMR spectra of these complexes confirm the low-spin d⁶ ground states of the metal centers.     

Topoisomerase II inhibition activity of new square planar Ni(II) complexes containing N-substituted thiosemicarbazones: Synthesis, spectroscopy, X-ray crystallography and electrochemical characterization

New Ni(II) thiosemicarbazone complexes containing triphenylphosphine namely [Ni(Sal-mtsc)(PPh₃)](2) and [Ni(Nap-mtsc)(PPh₃)] (3) (where Sal-mtsc = salicylaldehyde-N(4)-methylthiosemicarbazone and Nap-mtsc = 2-hydroxy-1-naphthaldehyde-N(4)-methylthiosemicarbazone) have been synthesised and characterized by elemental analysis, IR, electronic and ¹H NMR spectroscopy. The crystal structures of the complexes have been determined by single crystal X-ray diffraction technique. In all the complexes the thiosemicarbazone ligand coordinated to nickel through ONS mode. The electrochemical behavior of the complexes has been investigated by using cyclic voltammetry in acetonitrile. The new complexes were subjected to test their DNA topoisomerase II inhibition efficiency. The complex [Ni(Nap-mtsc)(PPh₃)] (3) showed 95% inhibition. The observed inhibition activity was found to be more potent than the activity of conventional standard Nalidixic acid.     

Copper(I) and silver(I) tertiary phosphines complexes: Synthesis, X-ray structures and spectroscopic characterization

Six new complexes, [Cu₄I₄(PPh₂Cy)₄]·2H₂O (1), [CuI(PPhCy₂)₂] (2), [CuCl(PPhCy₂)₂] (3), and [CuBr(PPh₃)₃]·CH₃CN (4), [Ag(PPhCy₂)₂(NO₃)] (5), [Ag(PCy₃)(NO₃)]₂ (6) [where Ph = phenyl, Cy = cyclohexyl], have been synthesized and structurally characterized by X-ray diffraction, IR absorption spectra and NMR spectroscopic studies (except complex 4). The X-ray diffraction analysis of complex (1), pseudo polymorph of complex [Cu₄I₄(PPh₂Cy)₄], reveals a stella quadrangula structure. The four corners of the cube are occupied by copper(I) atoms and four I atoms are present at the alternative corners of the cube, further more the copper(I) atoms are coordinated to a monodentate tertiary phosphine. Complexes (2) and (3) are isostructural with trigonal planar geometry around the copper(I) atom. The crystal structure of complex (4) is a pseudo polymorph of complex [CuBr(PPh₃)₃] and the geometrical environment around the copper(I) centre is distorted tetrahedral. In the Ag^I complexes (5) and (6), the central metal atoms have pseudo tetrahedral and trigonal planar geometry, respectively. Spectroscopic and microanalysis results are consistent with the single crystal X-ray diffraction studies.     

Synthesis, structure and electronic spectra of new three-coordinated copper(I) complexes with tricyclohexylphosphine and diimine ligands

Three new copper(I) complexes with tricyclohexylphosphine (PCy₃) and different diimine ligands, [Cu(phen)(PCy₃)]BF₄ (1) (phen = 1,10′-phennanthroline), [Cu(bpy)(PCy₃)₂]BF₄ (2) (bpy = 2,2′-bipyridine) and [Cu(MeO-CNN)(PCy₃)]BF₄ (3) (MeO-CNN = 6-(4-methoxyl)phenyl-2,2′-bipyridine), have been synthesized and characterized. X-ray structure reveals that complexes 1 and 3 are three-coordinated with trigonal geometry, while complex 2 adopts distorted tetrahedron geometry. Complexes 1 and 3 exhibit ligand redistribution reactions in chloromethane solution by addition of excess amount of PCy₃, in which three-coordinated 1 changes into four-coordinated [Cu(phen)(PCy₃)₂]⁺, and 3 leads to form [Cu(PCy₃)₂]BF₄ and CNN-OMe. All the three complexes display yellow ³MLCT emissions in solid state at room temperature with λ_max at 558, 564 and 582 nm for 1, 2 and 3, respectively, and red-shift to 605, 628 and 643 nm at 77 K in dichloromethane solution.     

Rh and Ir dibenzo[a,e]cyclooctatetraene complexes: Chloro, hydroxo, and mixed Au oxo complexes

New and improved procedures are reported for the synthesis of [M(DBCOT)(μ-Cl)]₂ (M = Rh, Ir; DBCOT = dibenzo[a,e]cyclooctatetraene) from MCl₃(H₂O)_x or [M(COD)(μ-Cl)]₂ and DBCOT. Treatment of [M(DBCOT)(μ-Cl)]₂ with [(LAu)₃(μ-O)]BF₄(L = PPh₃, P^tBu₃) yields the mixed-metal oxo complexes [M(DBCOT)(μ⁴-O)(AuL)₂]₂(BF₄)₂. Dimeric [Rh(DBCOT)(μ-OH)]₂ is obtained from the reaction of [M(DBCOT)(μ-Cl)]₂ with KOH in EtOH/H₂O. All complexes except [Rh(DBCOT)(μ-Cl)]₂ have been structurally characterized by single crystal X-ray diffraction.     

Synthesis and structural characterization of copper(I) complexes bearing N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA): Cytotoxic activity evaluation of a series of water soluble Cu(I) derivatives containing PTA, PTAH and mPTA ligands

New copper(I) complexes containing the water soluble N-methyl-1,3,5-triaza-7-phosphaadamantane (mPTA) phosphine have been synthesized by ligand-exchange reactions starting from [Cu(CH₃CN)₄][BF₄] or [Cu(CH₃CN)₄][PF₆] precursors and (mPTA)X (X = CF₃SO₃, I). Depending on the ligand counter ion, the hydrophilic [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a and [Cu(mPTA)₄][(CF₃SO₃)₄(PF₆)] 3c complexes or the iodine-coordinated [Cu(mPTA)₃I]I₃4 species were obtained respectively and fully characterized by spectroscopic methods. Single crystal structural characterization was undertaken for [Cu(mPTA)₃I]I₃·H₂O, 4·H₂O, and [Cu(mPTA)₄][(CF₃SO₃)₂(BF₄)₃] ·0.25H₂O, 3b·0.25H₂O, the latter obtained by crystallization of [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a. The cytotoxicity of analogous tetrahedral homoleptic Cu(I) derivatives [Cu(PTA)₄](BF₄) 1, [Cu(PTAH)₄][Cl₄(BF₄)] 2, [Cu(mPTA)₄][(CF₃SO₃)₄(BF₄)] 3a and [Cu(mPTA)₄][(CF₃SO₃)₄(PF₆)] 3c was evaluated against a panel of several human tumor cell lines. All the complexes showed in vitro antitumor activity comparable to that of the reference metallodrug cisplatin. Tests performed on cisplatin sensitive and resistant cell lines showed that against human ovarian 2008/C13^* cell line pair, the resistance factor of copper derivatives was roughly 7-fold lower than that of cisplatin, whereas against human cervix cancer A431/A431-Pt cell line pair it was about 2.5-fold lower. These results, confirming the circumvention of cisplatin resistance, support the hypothesis that phosphine copper(I) complexes follow different cytotoxic mechanisms than do platinum drugs.     

Coordination polymers of 1,8-bis(2-methylthioethoxy)anthraquinone and 1,5-bis(2-methylthioethoxy)anthraquinone with Ag(I): Synthesis and X-ray crystallography

The reaction of 2-(methylthioethanol) with 1,8-dichloroanthraquinone and 1,5-dichloroanthraquinone in THF with base produces 1,8-bis(2-methylthioethoxy)anthraquinone (1) and 1,5-bis(2-methylthioethoxy)anthraquinone (2), respectively. Silver(I) complexes of 1 and 2 have been synthesized after combination with [Ag(CH₃CN)₄]BF₄ in 1:1 M ratio to yield, [(1,8-bis(2-methylthioethoxy)anthraquinone)Ag]BF₄, (3) and [(1,5-bis(2-methylthioethoxy)anthraquinone)Ag·CH₃CN]BF₄, (4). X-ray crystal structures of the free ligand (1) and the Ag(I) complexes (3 and 4) are reported. The intraannular carbonyl group forms a coordinate-covalent bond with Ag(I) and, in the solid state, both silver(I) complexes are found as coordination polymers.     

Quantification of cis and trans influences in [PtX(PPh3)3] complexes. A P NMR study

In [PtX(PPh₃)₃]⁺ complexes (X = F, Cl, Br, I, AcO, NO₃, NO₂, H, Me) the mutual cis and trans influences of the PPh₃ groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P_(cis) and P_(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh₃)₃](BF₄) (2), [PtI(PPh₃)₃](BF₄) (3), [Pt(AcO)(PPh₃)₃](BF₄) (4), [Pt(NO₃)(PPh₃)₃](BF₄) (5), and the two isomers [Pt(NO₂-O)(PPh₃)₃](BF₄) (6a) and [Pt(NO₂-N)(PPh₃)₃](BF₄) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH₂Cl₂·0.25C₃H₆O have been determined. From the ¹J_PtP values of all compounds we have deduced the series: I > Br > Cl > NO₃ > ONO > F > AcO > NO₂ > H > Me (cis influence) and Me > H > NO₂ > AcO > I > ONO > Br > Cl > F > NO₃ (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh₃)₂] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.     

Coordination chemistry of the metalloligand [Pt2(μ-S)2(PPh3)4] with nickel(II) complexes - an electrospray mass spectrometry directed synthetic study

The reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards a range of nickel(II) complexes has been probed using electrospray ionisation mass spectrometry coupled with synthesis and characterisation in selected systems. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [Ni(NCS)₂(PPh₃)₂] gives [Pt₂(μ-S)₂(PPh₃)₄Ni(NCS)(PPh₃)]⁺, isolated as its BPh₄ ⁻ salt; the same product is obtained in the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [NiBr₂(PPh₃)₂] and KNCS. An X-ray structure determination reveals the expected sulfide-bridged structure, with an N-bonded thiocyanate ligand and a square-planar coordination geometry about nickel. A range of nickel(II) complexes NiL₂, containing β-diketonate, 8-hydroxyquinolinate, or salicylaldehyde oximate ligands react similarly, giving [Pt₂(μ-S)₂(PPh₃)₄NiL]⁺ cations.     

Synthesis, characterization and structural studies of new palladium(II) complexes including non-symmetric phosphorus ylides

The reaction of the non-symmetric phosphorus ylides, Ph₂P(CH₂)_nPPh₂C(H)C(O)PhR [Y₁-Y₄: n = 1, R = Cl, Br, NO₂, OCH₃ and Y₅-Y₈: n = 2, R = Cl, Br, NO, OCH₃] with dichloro(1,5-cyclooctadiene)palladium(II) in dichloromethane under mild conditions afford the monomeric P-C chelated complexes, [(Y)PdCl₂] (Y = Y₁-Y₈). These complexes were fully characterized by elemental analysis and spectroscopic techniques such as IR, ¹H, ³¹P, and ¹³C NMR. In addition, the identity of complexes [(Y₅)PdCl₂] (1b) and [(Y₈)PdCl₂] (4b) was unequivocally determined by single crystal X-diffraction techniques, both structures consisting of six-membered rings formed by coordination of the ligands through the phosphine group and the ylidic carbon atom to the metal center. The coordination geometry around the Pd atoms in both these complexes be defined as slightly distorted square planar. Furthermore, their electrochemical behavior was also investigated by cyclic voltammeters, thus the cyclic voltammetry of complex [(Y₁)PdCl₂], in dichloromethane solution with Pt electrode, shows that the redox reaction of the pair Pd(II)/Pd(0) is irreversible with the cathodic peak potential at −1.08 V versus Ag wire.     

Novel carbon-centered heteroscorpionate ligands: Cu(I) complexes and luminescence properties

Herein, we describe the synthesis of N,N′,S donor ligands 2-(1-(3,5-diisopropyl-1H-pyrazol-1-yl)-3-(methythio)propyl)-4-methoxy-3,5-dimethylpyridine (L1) and 2-(1-(3,5-diisopropyl-1H-pyrazol-1-yl)-2-(methythio)ethyl)-4-methoxy-3,5-dimethylpyridine (L2). Cu(I) complexes were prepared by reacting L1 or L2 with [Cu(CH₃CN)₄]BF₄ or CuCl. The coordination behavior of the thioether arm of the ligands was found to determine the nuclearity of the resulting complexes, in which [Cu(L1)PPh₃]BF₄ (1) is polynuclear, [Cu(L2)PPh₃]BF₄ (2) is mononuclear, while [Cu(L1)]₂(BF₄)₂ (3), [Cu(L2)CH₃CN]₂(BF₄)₂ (4), and [Cu(L1)Cl]₂ (5) are dinuclear. In the dimeric complex [Cu(L2)Cl]₂ (6), the sulfur atoms are not metal-bound. Rather, the two bridging chloride ions link the two copper centers. Compounds 4-6 are luminescent in the solid state, and exhibit emission bands centered at 490 nm (4), 544 nm (5), and 562 nm (6), respectively. Their excitation spectra display bands at 280 nm and 380 nm. According to DFT calculations, the HOMO is distributed partially over the metal centers and partially over the chloride anions (5 and 6) or the sulfur atoms (4) of the ligands, while the LUMO is a π∗ antibonding pyridine orbital. This suggests that the emission properties are derived from metal-to-ligand charge-transfer (MLCT), halide-to-ligand charge-transfer (XLCT), and ligand-to-ligand charge-transfer (LLCT) excited states.     

Influence of chain length on mono- versus di-alkylation in the reactivity of [Pt2(μ-S)2(PPh3)4] towards α,ω-dihalo-n-alkanes; a synthetic route to platinum(II) ω-haloalkylthiolate complexes

The reactions of [Pt₂(μ-S)₂(PPh₃)₄] with α,ω-dibromoalkanes Br(CH₂)_nBr (n = 4, 5, 6, 8, 12) gave mono-alkylated [Pt₂(μ-S){μ-S(CH₂)_nBr}(PPh₃)₄]⁺ and/or di-alkylated [Pt₂(μ-S(CH₂)_nS}(PPh₃)₄]²⁺ products, depending on the alkyl chain length and the reaction conditions. With longer chains (n = 8, 12), intramolecular di-alkylation does not proceed in refluxing methanol, with the mono-alkylated products [Pt₂(μ-S){μ-S(CH₂)_nBr}(PPh₃)₄]⁺ being the dominant products when excess alkylating agent is used. The bridged complex [{Pt₂(μ-S)₂(PPh₃)₄}₂{μ-(CH₂)₁₂}]²⁺ was accessible from the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with 0.5 mol equivalents of Br(CH₂)₁₂Br. [Pt₂(μ-S){μ-S(CH₂)₄Br}(PPh₃)₄]⁺ can be cleanly isolated as its BPh₄⁻ salt, but undergoes facile intramolecular di-alkylation at −18 °C, giving the known species [Pt₂(μ-S(CH₂)₄S}(PPh₃)₄]²⁺. The reaction of I(CH₂)₆I with [Pt₂(μ-S)₂(PPh₃)₄] similarly gives [Pt₂(μ-S){μ-S(CH₂)₆I}(PPh₃)₄]⁺, which is fairly stable towards intramolecular di-alkylation once isolated. These reactions provide a facile route to ω-haloalkylthiolate complexes which are poorly defined in the literature. X-ray crystal structures of [Pt₂(μ-S){μ-S(CH₂)₅Br}(PPh₃)₄]BPh₄ and [Pt₂(μ-S(CH₂)₅S}(PPh₃)₄](BPh₄)₂ are reported, together with a study of these complexes by electrospray ionisation mass spectrometry. All complexes fragment by dissociation of PPh₃ ligands, and the bromoalkylthiolate complexes show additional fragment ions [Pt₂(μ-S){μ-S(CH₂)_n−2CHCH₂}(PPh₃)_m]⁺ (m = 2 or 3; m ≠ 4), most significant for n = 4, formed by elimination of HBr.     

Study on synthesis, structure, and DNA-binding of Ni, Zn complexes with 2-phenylquinoline-4-carboylhydrazide

2-Phenylquinoline-4-carboylhydrazide (HL), and its novel nickel(II), zinc(II) complexes [M(HL)₂(L)]·2H₂O·NO₃ (M = Ni (1), M = Zn (2)), have been synthesized and characterized by elemental analysis, molar conductivity, and IR spectra. The crystal structure of [Ni(HL)₂(L)]·2H₂O·NO₃ obtained from ethanol solution was determined by X-ray diffraction analysis, crystallized in the rhombohedral system, space group , Z = 18, a = 31.913(3) Å, b = 31.913(3) Å, c = 27.709(2) Å, α = 90°, β = 90°, γ = 120°, R₁ = 0.0647. The interactions of the complexes and the ligand with calf thymus DNA had been investigated using UV-Vis spectra, fluorescent spectra, CD (circular dichroism) spectra, CV (cyclic voltammetry) and viscosity measurements. These compounds were tested against MFC (mouse forestomach carcinoma) cell lines. The complex 1 showed significant cytotoxic activity against MFC cell lines. The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. Results suggest that the two complexes bound to DNA via a groove binding mode and the complexes can cleave pBR322 DNA.     

Nickel and copper complexes based on tridentate nitrogen donor ligand 2,6-bis-(1-phenyliminoethyl) pyridine: Synthesis, spectral and structural characterization

The reaction of CuCl₂ · 2H₂O with 2,6-bis(1-phenyliminoethyl)pyridine (referred hereafter as L) in 1:1 molar ratio in methanol or acetronitrile at room temperature afforded distorted trigonal-bipyramidal complex [Cu(κ³-L)Cl₂]. On the other hand, the reaction of NiCl₂ · 6H₂O with 2 equivalents of L gave an octahedral complex [Ni(κ³-L)₂]²⁺, which was isolated as [Ni(κ³-L)₂][BF₄]₂ using NH₄BF₄. The complexes have been characterized by elemental analyses, FAB-MS, IR, EPR and electronic spectral studies. Molecular structures of both the [Cu(κ³-L)Cl₂] (1) and [Ni(κ³-L)₂](BF₄)₂ (2) have been determined by single crystal X-ray analyses. Weak interaction studies on 1 and 2 revealed stabilisation of the crystal packing by inter and intra-molecular C-H?X (X = F, Cl, π) interactions. In complex 2 ortho C-H bond from phenyl rings leads to unexpected C-H?π interaction with nickel α,α′-diimine chelate ring. This provides structural support for metalloaromaticity in the chelate ring of complex 2.     

Copper(I) complexes with Schiff base and 1,2-bis(diphenylphosphino)ethane as ligands: Synthesis, structure and catalytic properties for the amination of aryl halide

Some copper(I) complexes of the type [Cu(L)(dppe)]X (1-4) [where L = (3-trifluoromethylphenyl)pyridine-2-ylmethylene-amine; dppe = 1,2-bis(diphenylphosphino)ethane; X = Cl⁻, CN⁻, ClO₄⁻ and BF₄⁻] have been synthesized by the condensation of 3-aminobenzotrifluoride with 2-pyridinecarboxaldehyde followed by the reaction with CuCl, CuCN, [Cu(MeCN)₄]ClO₄ and [Cu(MeCN)₄]BF₄ in presence of dppe. The complexes 1-4 were then characterized on the basis of elemental analysis, IR, UV-Vis and ¹H NMR spectral studies. The representative complex of the series 4 has been characterized by single crystal X-ray diffraction which reveal that in complex the central copper(I) ion assumes the irregular pseudo-tetrahedral geometry. The catalytic activity of the complexes was tested and it was found that all the complexes worked as effective catalyst in the amination of aryl halide.     

Synthesis of [SnPh2(SR)2] SR = SC6F4-4-H, SC6F5: Reactivity towards group 10 transition metal complexes

The organometallic tin(IV) complexes [SnPh₂(SR^F)₂] SR^F = ⁻SC₆F₄-4-H (1), ⁻SC₆F₅ (2), were synthesized and their reactivity with [MCl₂(PPh₃)₂] M = Ni, Pd and Pt explored. Thus, transmetallation products were obtained affording polymeric [Ni(SR^F)(μ-SR^F)]_n, monomeric cis-[Pt(PPh₃)₂(SC₆F₄-4-H)₂] (3) and cis-[Pt(PPh₃)₂(SC₆F₅)₂] (4) and dimeric species [Pd(PPh₃)(SC₆F₄-4-H)(μ-SC₆F₄-4-H)]₂ (5) and [Pd(PPh₃)(SC₆F₅)(μ-SC₆F₅)]₂ (6) for Ni, Pt and Pd, respectively. The crystal structures of complexes 1, 2, 3, 4 and 6 were determined.