Syntheses and structural characterization of dicopper(I) bis(diphenylphosphino)acetylene complexes containing tricyclic, cyclic and linear frameworks

The complexes [Cu₂(dppa)₃(CH₃CN)₂][BF₄]₂ (1) and Cu₂(dppa)₃(O₃SCF₃)₂ (2) have been prepared in good yields by treating [Cu(MeCN)₄][BF₄] and [Cu(MeCN)₄][O₃SCF₃], respectively, with Ph₂PCCPPh₂ (abbreviated as dppa) at room temperature. The reaction of 1 with di-2-pyridyl ketone (abbreviated as dpyk) produces [Cu₂(dppa)₂(dpyk)₂][BF₄]₂ (3), and with 1,1′-bis(diphenylphosphino)ferrocene (abbreviated as dppf) produces [Cu₂(dppa)(dppf)₂][BF₄]₂ (4). The molecular structures of 1-4 have been determined by an X-ray diffraction study. Compounds 1 and 2 form a helical Cu₂(dppa)₃ metallatricycle, compounds 3 forms a Cu₂(dppa)₂ metallacycle, and compound 4 contains a linear Cu₂(dppa) skeleton.     

Synthesis, characterization, crystal structures and photophysical properties of copper(I) complexes containing 1,1′-bis(diphenylphosphino)ferrocene (B-dppf) in doubly-bridged mode

Five copper(I) complexes having general formula [Cu₂(μ-X)₂(κ²-P,P-B-dppf)₂] (X = Cl(1), Br(2), I(3), CN(4), and SCN(5)) were prepared starting with CuX and B-dppf in 1:1 molar ratio in DCM-MeOH (50:50 V/V) at room temperature. The complexes have been characterized by elemental analyses, IR, ¹H NMR, ³¹P NMR and electronic spectral studies. Molecular structures for 1, 2 and 4 were determined crystallographically. Complexes 1, 2 and 4 exist as centrosymmetric dimers in which the two copper atoms are bonded to two bridging B-dppf ligands and two bridging (pseudo-)halide groups in a μ-η¹ bonding mode to generate nearly planar Cu₂(μ-η¹-X)₂ framework. Both bridging B-dppf ligands are arranged in antiperiplanar staggered conformation in 1 and 2 (mean value 56.40-56.76°), and twisted from the eclipsed conformation (mean value 78.19°) in 4. The Φ angle value in 4 is relatively larger as compared to 1 and 2. This seems to indicate that the molecular core [Cu₂(μ-η¹-X)₂] in 4 is a sterically demanding system that forces the B-dppf ligand to adopt a relatively strained conformation in comparison to less strained system in 1 and 2. All the complexes exhibit moderately strong luminescence properties in the solution state at ambient temperature.     

Heteroleptic Cu(I) complexes containing phenanthroline-type and 1,1′-bis(diphenylphosphino)ferrocene ligands: Structure and electronic properties

Three new heteroleptic Cu(I) complexes containing one phenanthroline and one diphosphine type ligand ([Cu(N-N)(P-P)]⁺) have been prepared. In particular, one ligand is constituted by 1,10-phenanthroline (1), 2,9-dimethyl-1,10-phenanthroline (2) and 2,9-diphenethyl-1,10-phenanthroline (3) and the other ligand is in all cases 1,1′-bis(diphenylphosphino)ferrocene (dppf). Therefore, copper and iron metal centres are quite close one another, as evidenced by X-ray crystal diffraction. The structure together with the electrochemical and photophysical properties of these complexes have been compared to that of the corresponding complexes where dppf has been replaced by bis[2-(diphenylphosphino)-phenyl]ether (POP). Cyclic voltammetric experiments evidenced that the first oxidation process is located on the ferrocene moiety and that oxidation of Cu(I) is moved to more positive potential values and a chemical reaction is coupled to the electron transfer process. The absorption spectra show a metal-to-ligand charge transfer (MLCT) band, typical of Cu(I) phenanthroline complexes, at a higher energy compared to the homoleptic [Cu(N-N)₂]⁺ species. No emission at either room temperature or 77 K has been observed for compounds 2 and 3, contrary to the high luminescence observed for the corresponding POP complexes. This result is consistent with a photoinduced energy transfer from the Cu(I) complex to the ferrocene moiety.     

Diphosphines as bridging ligands in polymeric and dimeric thione-S-ligated Ag(I) nitrate complexes

Reactions of silver(I) nitrate with equimolar amounts of the diphos ligands 1,4-bis(diphenylphosphino)butane (dppb) or 1,2-bis(diphenylphosphino)ethane (dppe) and some heterocyclic thiones (L) in acetonitrile/methanol solvent afforded mixed-ligand complexes, the nature of which was found to be strongly influenced by the backbone length of the diphosphine ligand. The longer chained diphos ligand formed a series of dinuclear complexes of the type [Ag(dppb)(L)]₂(NO₃)₂ with both the diphosphine and thione ligands acting as bridging ligands between the two four-coordinate pseudo-tetrahedrally coordinated metal centers. In the unique case of L=4-methyl-5-trifluoromethyl-4H-1,2,4-triazoline-3(2H)-thione (mftztH), the reaction proceeded under exclusion of the thione ligand from the coordination sphere and coordination of the nitrate anions instead, leading to the diphosphine-doubly bridged dimeric compound [Ag(dppb)(NO₃)]₂. On the other hand, the complexes produced when using the short bite 1,2-bis(diphenylphosphino)ethane (dppe) turned out to be diphosphine-bridged cationic polymers of the type [Ag(dppe)(L)₂]_n(NO₃)_n. The structures of one representative for each of the two aforementioned series of complex compounds, namely [Ag(dppb)(py2SH)]₂(NO₃)₂ · 2H₂O and [Ag(dppe)(pymtH)₂]_n(NO₃)_n, have been established by single-crystal X-ray diffraction.     

Trans-1,2-bis(diphenylphosphino)ethene as bridging ligand in thione-S-ligated dimeric copper(I) chloride complexes

Several mixed-ligand complexes have been prepared by treatment of copper(I) chloride with equimolar amounts of trans-1,2-bis(diphenylphosphino)ethene (trans-dppen) in acetonitrile followed by the addition of a methanolic solution of one equivalent of a heterocyclic thione (L). The novel complex compounds have been characterized by single-crystal X-ray diffraction, ¹H NMR and IR spectroscopy as well as by elemental analyses and melting points. The X-ray structures of three examples confirm that the compounds are homobimetallic dimers of type [CuCl(μ₂-trans-dppen)(L)]₂ containing two tetrahedral coordination units joined by two trans-dppen bridges.     

Construction of one-, two- and three-dimensional Cu(I) polymeric architectures containing bis(diphenylphosphino)acetylene and 4,4′-bipyridine linking ligands

One-dimensional {[Cu₂(dppa)₂(4,4′-bipy)(CH₃CN)₂](BF₄)₂ · 2CH₃CN}_n (1), two-dimensional {[Cu₂(dppa)(4,4′-bipy)₂(CH₃CN)₂](BF₄)₂ · 4CH₂Cl₂ · 4H₂O}_n (2) and three-dimensional {[Cu₂(dppa)(4,4′-bipy)₃](BF₄)₂ · 2CH₂Cl₂ · 3CH₃CN · 3H₂O}_n (3) polymeric complexes have been prepared by self-assembly of [Cu(MeCN)₄]BF₄, Ph₂PCCPPh₂ (dppa) and 4,4′-bipyridine (4,4′-bipy) in a 2:2:1, 1:1:1 and 2:2:3 molar ratio, respectively. The structures of 1-3, determined by an X-ray diffraction study, reveal a linear spring-like architecture for 1, a planar honeycomb grid for 2 and an interlocked adamantoid network for 3.     

Copper(I) halide complexes from cis-1,2-bis(diphenylphosphino) ethylene and some heterocyclic thiones

Reaction of copper(I) chloride or bromide with equimolar amounts of the diphos ligand cis-1,2-bis(diphenylphosphino)ethylene (dppet) and a heterocyclic thione (L) in acetonitrile/methanol solvent afforded mononuclear complexes of the type [CuX(dppet)(L)] with the diphosphine ligand acting as a chelating ligand. However, the same reaction carried out at higher temperatures proceeds, in some cases, with exclusion of the phosphine ligand from the coordination sphere leading to double-S-bridged dimers. In contrast, copper(I) iodide under the same conditions gave the thione-free dimeric compound [CuI(dppet)]₂ which contains double-bridging iodine atoms. A notable exception was for the reaction with 5-methyl-1,3,4-thiadiazole-2-thione (mtdztH) which, under the same conditions, gave rise to the unexpected, simultaneous formation of the monomer [CuI(dppet)(CH₃CN)] as well as the above mentioned dimeric [CuI(dppet)]₂. Furthermore treatment [CuX(dppet)(L)] with two equivalents of triphenylphosphine was found to cause replacement of the diphos ligand, while substitution of the chlorine atom under HCl elimination and formation of [Cu(dppet)(mftztH)₂] occured in the unique case of treating [CuCl(dppet)(mftztH)] with one additional equivalent of the same thione ligand. The structures of one representative for each of the above mentioned types of complexes, namely [CuBr(dppet)(mftztH)], [Cu(dppet)(mftztH)₂], [Cu(μ-I)(dppet)]₂ · [CuI(dppet)(CH₃CN)] and [CuBr{μ-S(pymtH)}(pymtH)]₂ have been established by single-crystal X-ray diffraction.     

Syntheses, characterization and crystal structures of copper(I) o-(diphenylphosphino)benzaldehyde complexes

The complexes [Cu(PCHO)₂(NCMe)][BF₄] (1) and [Cu(PCHO)₃][BF₄] (2) have been prepared by treating [Cu(NCMe)₄][BF₄] with two and three equivalents of Ph₂P(o-C₆H₄)C(O)H (abbreviated as PCHO) at room temperature, respectively. The reaction of 1 and (Ph₂PC₅H₄)₂Fe (abbreviated as DPPF) affords [Cu(PCHO)(DPPF)][BF₄] (3). The molecular structures of 1-3 have been determined by an X-ray diffraction study. The aldehyde groups in 1 are pendant, while one of the formyl groups in 2 is weakly coordinated to the copper ion through the oxygen atom. On the other hand, the copper atom in 3 is strongly chelated by both DPPF and PCHO ligands.     

Photoluminescent coordination polymers of d metals with 4,4′-dipyridylsulfide (dps)

Reactions of AgClO₄, Zn(CH₃COO)₂ · H₂O and CuI with the ligand 4,4′-dipyridylsulfide (dps) in 1:1 ratio give rise to coordination polymers 1-3 and 5, the structures of which were characterized by X-ray crystallography. Polymers [Ag₂(dps)₂](ClO₄)₂ · MeCN (1) and [Ag₂(dps)₂(μ₂-MeCN)(MeCN)](ClO₄)₂ · MeCN · H₂O (2) are pseudo-supramolecular isomers, differing from each other in the coordination geometry of silver atom and the packing pattern. Both 1 and 2 are zigzag coordination polymers bridged by weak Ag?Ag, Ag?S or Ag?NC-CH₃ interactions to form double stranded coordination polymers. While [Zn(dps)(CH₃COO)₂] (3) is a zigzag single stranded coordination polymer, [Zn(dps)₂(H₂O)₂](ClO₄)₂ · H₂O (4) is an unusual mononuclear complex with a box-like structure. Interesting intermolecular hydrogen bonding present in the compounds 3 and 4 leads to 3D hydrogen-bonded network structure.Coordination polymer [Cu₂I₂(dps)₂] (5) is a non-interpenetrating (4,4) net. Photoluminescence properties of the compounds 1-5 have been examined in solid states at room temperature. These compounds have been found to exhibit yellow and blue photoluminescence.     

Preparation and photophysical studies of copper(I) and ruthenium(II) complexes of 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine

We report the synthesis of a new ligand, 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine, optimised for binding to copper(I) and with pendant functionality that can eventually be developed into metallodendritic structures. The synthesis and photophysical properties of complexes with copper(I) and ruthenium(II) are reported. The solid state structure of the complex [Cu(1)₂][PF₆] · MeCN (1 = 4,4′-bis(3,5-dimethoxyphenyl)-6,6′-dimethyl-2,2′-bipyridine) is also described.     

Syntheses, crystal structures and properties of Cd(II) and Co(II) complexes with 4,4′-dipyridylsulfide ligand

Two new coordination polymers [Cd(dps)₂Cl₂] (1) and [Co(dps)₂(H₂O)₂]·(abs)₂(H₂O)₂ (2) (dps = 4, 4′-dipyridylsulfide, Habs = 4-amino benzenesulfonic acid) have been synthesized under similar conditions and characterized by elemental analysis, fluorescence spectra and single crystal X-ray diffraction. Compound 1 displays a dps-bridged 2D puckered, grid-like layer, which is further linked by C-H?Cl hydrogen bonds to form a 3D supramolecular architecture. Compound 2 shows a dps-bridged double-stranded chain structure, which is extended by N-H?O and O-H?O hydrogen bonds generating a 3D network. Solid-state fluorescence results reveal that both complexes can emit strong emission bands, at 467 nm and 518 nm for 1 and 344 nm for 2, respectively. Magnetic measurements show that there are weak antiferromagnetic interactions between the adjacent Co(II) ions in 2.     

Synthesis, structure and DNA cleavage activity of two 4,4′-dimethyl-2,2′-bipyridyl manganese(II) complexes

Two new mononuclear Mn(II) complexes, Mn(dmbpy)₂(OCN)₂ (1) and Mn(dmbpy)₂(dca)₂ (2) (dmbpy = 4,4′-dimethyl-2,2′-bipyridine, dca = dicyanamide), have been synthesized and characterized by IR, elemental analysis, and single crystal X-ray analysis. Both complexes have similar molecular structures. The coordination sphere of the Mn(II) ion in 1 or 2 is a seriously distorted octahedron formed by two dmbpy ligands and two OCN⁻ or dca anions in cis positions. For both complexes, the most striking feature is that the mononuclear molecules are linked together by plentiful weak C-H?N hydrogen bonds into a compact 3D supramolecular structure. DNA cleavage studies show that the complexes can promote plasmid DNA cleavage in the presence of H₂O₂ under physiological conditions, and their cleavage activities are obviously both pH value and complex concentration-dependent. The cleavage mechanism between the complexes and plasmid DNA is likely to involve hydroxyl radicals as reactive oxygen species.     

Synthesis and properties of Re(I) tricarbonyl complexes of 6,6′-disubstituted-4,4′-bipyrimidines with high energy excited states suitable for incorporation into polynuclear arrays

A series of complexes [(N-N)Re(CO)₃X]ⁿ (N-N = 6,6′-diaryl-4,4′-bipyrimidine, axial ligand X = Cl, MeCN, 4-phenyl-pyridine, or t-Bu-pyridine) have been synthesized and characterized. The substituent aryl on the bipyrimidine, as well as the axial ligand X, has important effects on the properties of these complexes. The co-planarity of the 4,4′-bipyrimidine core and its substituents contributes to the extent of π-electron delocalization and, hence, to the redox and spectroscopic properties of the complexes. The complexes exhibit Re-to-bpm metal-to-ligand charge transfer absorptions in the range of 379-464 nm, which are red-shifted with the increase in the delocalization in the substituted bpm ligand and the increase in the donor character of the axial ligand. The electrochemical data support metal-based oxidations (from +1.07 to +1.40 V) and ligand-based reductions (from −0.62 to −0.75 V) and correlate well with those obtained by UV-Vis spectroscopy. The X-ray crystal structures of two of the complexes have also been investigated.     

Synthesis, characterization and molecular structure of 1,1′ bis(diphenylphosphino ferrocene)dioxide complex of uranyl nitrate

A 1,1′ bis(diphenylphosphino ferrocene)dioxide complex of uranyl nitrate was synthesized and characterized by IR, ¹H and ³¹P{¹H} NMR spectroscopic and X-ray diffraction methods. The structure of the compound shows that the uranium atom is surrounded by eight oxygen atoms in a hexagonal bi-pyramidal geometry. Two oxygen atoms from 1,1′ bis(diphenylphosphino ferrocene)dioxide ligand and four oxygen atoms from the nitrate groups form a planar hexagon. The two uranyl oxygen atoms occupy the axial position. The 1,1′ bis(diphenylphosphino ferrocene)dioxide ligand acts as a bidentate chelating ligand with a bite angle of 71.56(8)° around the uranium(VI) atom, which is much smaller in value compare to any of the previously reported values (90.1°-154.0°) for this ligand.     

Chiral diruthenium(II) complexes containing a modified 4,4-bipyridine bridging ligand: syntheses, characterization and DNA binding

A pair of novel chiral dimeric ruthenium(II) complexes [ΔΔ-, ΛΛ-Ru(bpy)₂(btpb)Ru(bpy)₂]⁴⁺ (1; btpb=2,2^′-bis(1,2,4-triazino[5,6-f]phenanthren-3-yl)-4,4^′-bipyridine) have been synthesized and characterized by electrospray mass spectra, ¹H NMR, UV-Vis and circular dichroism spectra. Binding behaviors of the complexes with calf thymus DNA have been investigated by absorption spectra and viscosity measurements. The electronic absorption spectrum of ΔΔ-1 at 505.5 nm exhibits hypochromism of about 8.4% and bathochromism of 2.5 nm; ΛΛ-1 at 500.0 nm exhibits hypochromism of about 9.1% and bathochromism of 4.5 nm, respectively. The experiments suggest that ΔΔ-1 and ΛΛ-1 may be bound to DNA by non-intercalating binder.     

Spectroscopic and electrochemical properties of heteroleptic cationic copper complexes bis-(diphenylphosphino)alkane-(2,2′-biquinoline)copper(I). Crystal structure of bis(diphenylphosphino)ethane-(2,2′-biquinoline)copper(I) perchlorate

A series of [Cu^(I)(2,2′-biquinoline)(L)](ClO₄) complexes (L = bis(diphenylphosphino)methane (bppm), 1,2-bis(diphenylphosphino)ethane (bppe), 1,4-bis(diphenylphosphino)butane (bppb)) have been synthesized and characterized by elemental analysis, conductivity, ESI-mass, NMR and UV-Vis spectroscopies, cyclic voltammetry, X-ray diffraction ([Cu^(I)(2,2′-biquinoline)(bppe)](ClO₄)) and DFT calculations. These compounds are monometallic species in a distorted tetrahedral arrangement, in contrast with related compounds found as dinuclear according to diffraction studies. The spectroscopic properties are not directly correlated with the length of alkyl chain bridge between the bis-diphenylphosphine groups. In this way, the chemical shift of some 2,2′-biquinoline protons and the metal to ligand charge transfer (Cu to 2,2′-biquinoline) follows the order [Cu(2,2′-biquinoline)(bppm)](ClO₄), [Cu(2,2′-biquinoline)(bppb)](ClO₄), [Cu(2,2′-biquinoline)(bppe)](ClO₄). The same dependence is followed by the potentials to Cu(II)/Cu(I) couple. These results are discussed in terms of inter-phosphorus alkane chain length and tetrahedral distortions on copper.     

Syntheses and electrochemical properties of ruthenium(II) complexes with 4,4-bipyrimidine and 4,4-bipyrimidinium ligands

The syntheses and electrochemical properties of novel ruthenium(II) polypyridyl complexes with 4,4^′-bipyrimidine, [Ru(trpy)(bpm)Cl](X) ([1](X; X=PF₆⁻, BF₄⁻)) and with a quaternized 4,4^′-bipyrimidinium ligand, [Ru(trpy)(Me₂bpm)Cl](BF₄)₃ ([2](BF₄)₃) (trpy=2,2^′:6^′,2″-terpyridine, bpm=4,4^′-bipyrimidine, Me₂bpm=1,1^′-dimethyl-4,4^′-bipyrimidinium) are presented. The bpm complex [1]⁺ was prepared by the reaction of Ru(trpy)Cl₃ with 4,4^′-bipyrimidine in EtOH/H₂O. The structural characterization of [1]⁺ revealed, that the bpm ligand coordinated to the ruthenium atom with the bidentate fashion. Diquaternization of the non-coordinating nitrogen atoms on bpm of [1]⁺ by (CH₃)₃OBF₄ in CH₃CN gave [2](BF₄)₃. The electrochemical and spectroelectrochemical properties of the complexes are described.     

Coordination chemistry of Re complexes with 2(2′-pyridyl)benzimidazole

Two new Re(III) and Re(IV) complexes with 2(2′-pyridyl)benzimidazole (pbimz) were prepared and their crystal and molecular structures established by single-crystal X-ray diffraction. Reaction of [ReOCl₂(OEt)(PPh₃)₂] with the ligand gave red cis(Cl),trans(P)-[ReCl₂(PPh₃)₂(pbimz)]Cl (1), while red [ReCl₄(pbimz)] · OPPh₃ (2) was obtained from [ReCl₃(PhC(O)C(O)Ph)(PPh₃)] and pbimz in the presence of perchlorate. The compounds were characterized by elemental analysis, FAB-MS, UV-Vis, IR, NMR spectroscopy and magnetic susceptibility measurements.     

Reversible photochromism of novel silver(I) coordination complexes with 1,2-bis(2′-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene in crystalline phase

Three novel silver(I) complexes with 1,2-bis(2-methyl-5′-(2″-pyridyl)-3′-thienyl)perfluorocyclopentene (BM-2-PTP) were synthesized by the reaction of Ag(CF₃SO₃) or Ag(CF₃COO) with BM-2-PTP in benzene at different temperatures. The structures of these metal complexes were revealed by X-ray crystallographic analyses and the correlation between crystal structures and photochromic performance was discussed. In complexes 1 and 2, silver(I) is three-coordinated to two nitrogens from distinct ligand molecules as well as one oxygen from anions to form a 1-D polymeric structure. On the other hand, complex 3 contains two crystallographic independent Ag(I) with different coordination environments, and the adjacent BM-2-PTP molecules are connected by Ag-CF₃CO₂-Ag chains to afford a 1-D double chain structure. The difference in structures of three complexes shows the interesting anionic effect on coordination and the subtleness of crystal engineering. It is noted that complex 3 underwent reversible photochromic reaction in crystalline state despite the unfavorable framework to the rotation of thiophene groups.     

Supramolecular architectures constructed on the skeleton of Silver nitrate, 4,4′-bipyridine and triphenylphosphine/1,2-bis(diphenylphosphino)ethane: Synthesis, structural characterization and non-covalent interactions

In the presence of PPh₃ and Ph₂PCH₂CH₂PPh₂ (dppe); AgNO₃ and 4,4′-bipyridine (bpy) react to form [Ag(PPh₃)(bpy)_1/2(ONO₂)]_n (1) and [Ag(dppe)_1/2(bpy)_1/2(ONO₂)]_n (2). The compositions of these complexes are supported by their elemental analysis. The structures are determined by spectroscopic (IR, ¹H NMR, UV-Vis) and X-ray crystallographic data. A zig-zag ladder type structure observed in 1 changes into straight ladder type structure in 2 in which [Ag(dppe)_1/2(ONO₂)]_n chains are bridged by bpy with Ag?Ag distance of 11.48 Å. However in 1, the two zig-zag chains are linked via π-π interactions at 3.82 Å between phenyl rings of terminal PPh₃ ligands. Both complexes luminesce in DMSO solution. Photoluminescence of a representative complex 2 is also measured.