DNA photocleavage and anticancer activity of terpyridine copper(II) complexes having phenanthroline bases

Copper(II) complexes [Cu(ph-tpy)(B)](ClO₄) (1–3), where ph-tpy is (4′-phenyl)-2,2′:6′,2″-terpyridine and B is N,N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN₅ coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d–d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC₅₀ values are 3.7 and 12.4 μM in visible light of 400–700 nm and dark, respectively.     

Ruthenium monoterpyridine complexes with 2,6-bis(benzimidazol-2-yl)pyridine: Synthesis,spectral properties and structure

Ruthenium monoterpyridine complexes with the tridentate 2,6-bis(benzimidazol-2-yl)pyridine (LH₂), [Ru(trpy)(LH₂)]²⁺, [1]²⁺ and [Ru(trpy)(L²⁻)], 2 (trpy = 2,2′:6′,2″-terpyridine) have been synthesized. The complexes have been authenticated by elemental analyses, UV–Vis, FT-IR, ¹H NMR spectra and their single crystal X-ray structures. Complexes [1]²⁺ and 2 exhibit strong MLCT band near 475 and 509 nm, respectively, and are found to be very much dependent on solution pH. The successive pH dependent dissociations of the N–H protons of benzimidazole moiety of LH₂ in [1]²⁺ lead to the formation of 2. The proton induced inter-convertibility of [1]²⁺ and 2 has been monitored via UV–Vis spectroscopy and redox features. The two pK_a values, 5.75 and 7.70, for complex [1]²⁺ have been determined spectroscopically.     

Synthesis,spectral and magnetic properties of two different 2-nitrobenzoatocopper(II) complexes containing N,N-diethylnicotinamide

Two structurally different complexes, [Cu₂(2-NO₂Bz)₄(denia)₁]_n (1) and [Cu(2-NO₂Bz)₂(denia)₂(H₂O)₂] (2), were prepared from the same reaction (where 2-NO₂Bz = 2-nitrobenzoate, denia = N,N-diethylnicotinamide) and they are reported together with [Cu₂(2-NO₂Bz)₄(DMF)₂] (3) (DMF = N,N-dimethylformamide). The compounds under study were characterized by elemental analysis, electronic, IR and EPR spectra, magnetic measurements over the temperature range of 1.8–300 K and X-ray analysis. The molecular structure of (1) is polymeric, (2) is monomeric and (3) is dimeric. In the polymeric chain of (1), the denia molecules serve as bridges between dimeric Cu₂(2-NO₂bz)₄ units. Each Cu(II) atom has a square-pyramidal arrangement with different chromophores, Cu¹O₄O′ and Cu²O₄N. The Cu–Cu distances are 2.699(1) Å in the dimeric unit and 7.980(3) Å between the dimeric units. In (2) the Cu(II) atom has a tetragonal-bipyramidal environment CuO₂N₂O′₂. In (3) two Cu(II) atoms are bridged by four carboxylate groups of four 2-NO₂bz anions in a syn–syn arrangement which create a square base about each Cu(II) atom and an apical position is occupied by the O atom of a DMF molecule (CuO₄O′). The Cu–Cu distance of 2.633(1) Å is somewhat shorter than in (1). Spectral and magnetic data of the complexes are discussed with their structures.     

Complexes derived from the general copper(II)/maleamic acid/N,N′,N′′-chelate reaction systems: Synthetic,reactivity, structural and spectroscopic studies

The synthetic investigation of the Cu^II/maleamate(−1) ion (HL⁻)/N,N′,N′′-chelate general reaction system has allowed access to compounds [Cu₂(HL)₂(bppy)₂](ClO₄)₂·H₂O (1·H₂O), [Cu(HL)(bppy)(ClO₄)] (2) and [Cu(HL)(terpy)(H₂O)](ClO₄) (4) (bppy = 2,6-bis(pyrazol-1-yl)pyridine, terpy = 2,2′;6′,2′′-terpyridine). In the absence of externally added hydroxides, compound [Cu₂(L′)₂(bppy)₂](ClO₄)₂ (3) was obtained from MeOH solutions; L′⁻ is the monomethyl maleate(−1) ligand which is formed in situ via the Cu^II-assisted HL⁻ → L′⁻ transformation. In the case of tptz-containing (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) reaction systems, the Cu^II-assisted hydrolysis of tptz to pyridine-2-carboxamide (L1) afforded complex [Cu(L1)₂(NO₃)₂] (5). The crystal structures of 1–5 are stabilized by intermolecular hydrogen bonding and π–π stacking interactions. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Magneto-structural study on a series of rhenium(IV) complexes containing biimH2, pyim and bipy ligands

Three rhenium(IV) mononuclear compounds of formulae [ReCl₄(biimH₂)] · 2DMF (1), [ReCl₄(pyim)] · DMF (2) and [ReCl₄(bipy)] (3) (biimH₂ = 2,2′-biimidazole, pyim = 2-(2′-pyridyl)imidazole, bipy = 2,2′-bipyridine and DMF = N,N-dimethylformamide) have been prepared and characterized. The crystal structure of 2 was determined by single crystal X-ray diffraction. Compound 2 crystallizes in the monoclinic system with P2₁/c as space group. The rhenium atom is six-coordinated by four Cl atoms and two nitrogen atoms from a bidentate pyim ligand [average values of Re–Cl and Re–N bonds lengths being 2.330(2) and 2.117(4) Å, respectively]. The magnetic properties were investigated from susceptibility measurements performed on polycrystalline samples of 1–3 in the temperature range 1.9–300 K. The magnetic behaviour found is typical of antiferromagnetically coupled systems, and they exhibit susceptibility maxima at 2.8 (1 and 2) and 5.6 K (3). Short Re^IV–Cl?Cl–Re^IV contacts through space account for the antiferromagnetic behaviour observed.     

Synthesis,structure, optical and magnetic properties of [CrL(X)3], {L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine; X = Cl,N3, NCS}

Three complexes of composition [CrL(X)₃], where L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and X = Cl⁻, N₃⁻, NCS⁻ are synthesized. They are characterized by IR, UV–Vis, fluorescence, EPR spectroscopic, and X-ray crystallographic studies. Structural studies reveal that the Cr(III) ion is coordinated by three N atoms of L in a meridional fashion. The three anions occupy the other three coordination sites completing the mer-N₃Cl₃ (1) and mer-N₃N₃ (2 and 3), distorted octahedral geometry. The Cr–N2 has a shorter length than the Cr–N1 and Cr–N3 distances and the order Cr–N(NCS⁻) < Cr–N(N₃⁻) < Cr–Cl is observed. They exhibit some of the d–d transitions in the visible and intra-ligand transitions in the UV regions. The lowest energy d–d transition follows the trend [CrLCl₃] < [CrL(N₃)₃] < [CrL(NCS)₃] consistent with the spectrochemical series. In DMF, they exhibit fluorescence having π → π^∗ character. All the complexes show a rhombic splitting as well as zero-field splitting (zfs) in X-band EPR spectra at 77 K.     

Solvothermal syntheses and crystal structures of new Cu(II) complexes with phenylsuccinic acid

Five new Cu(II) complexes [Cu(psa)(phen)] · 3H₂O (1), [Cu(psa)(2bpy)] · 0.5H₂O (2), [Cu(psa)(2bpy)(H₂O)] · 3H₂O (3), [Cu(psa)(4bpy)] · H₂O (4), and [Cu(psa)_0.5(N₃)(2bpy)] (5) (H₂psa = phenylsuccinic acid, phen = 1,10-phenanthroline, 2bpy = 2,2′-bipyridine, and 4bpy = 4,4′-bipyridine) were obtained under solvothermal conditions and characterized by single-crystal X-ray diffraction. Complexes 2 and 3 were formed by one-pot reaction. In complex 2, Cu(II) ion is four-coordinated and locates at a slightly distorted square center. In complex 3, the coordinated water molecule occupies the axial site of Cu(II) ion forming a tetragonal pyramid geometry. Complexes 1 and 3 are of 1D chain structures, and extended into 2D supramolecular network by hydrogen bonds. Complex 2 is of zipper structure, and further assembled into 2D supramolecular network by hydrogen bonds and π–π stacking interactions. Complex 4 is a 3D CdSO₄-like structure with twofold interpenetration, while complex 5 is a dinuclear compound. The different structures of complexes 1–5 can be attributed to using the auxiliary ligands, indicating an important role of the auxiliary ligands in assembly and structure of the title complexes.     

Single stranded helical supramolecular architecture with a left handed helical water chain in ternary copper(II) tryptophan/diamine complexes

The ternary copper(II) complexes [Cu(l-trp)(bpy)](ClO₄) (1) and [Cu(l-trp)(phen)] (ClO₄) · 3H₂O (2) (where l-trp = l-tryptophan, bpy = bipridyl, phen = phenanthroline) have been synthesized. The single crystal X-ray structures for these complexes revealed that the monocationic Cu^II-units are interlinked through Cu–OCO–Cu connectivity and exist as helical coordination polymers. The two different helical strands composed with Cu1 and Cu2 independently, possess a similar pitch distance of 7.713 Å in complex 1. For complex 2, existing in the hydrated form, the Cu(II) polymeric strand and the hydrated water molecules have gained a supramolecular helical architecture with a similar pitch distance of 8.133 Å. The two helical strands in complex 1 are associated with right handed (PP) supramolecular chirality, while the helical water chain and the Cu^II-strand in 2 are self assembled into left handed (MM) helicity in the solid state. The solid state CD recorded for 1 and the dehydrated form of 2 exhibit a positive optical sign at their respective d–d band [λ_max = 667 nm, 1; λ_max = 630 nm, 2], the solution state CD for both these complexes are found to be inverted into a negative optical sign, which could be attributed to inversion of their associated supramolecular helicity. The TGA curve illustrates two distinct weight losses at 60 °C and 87 °C, equivalent to one and two water molecules, respectively. The PXRD pattern for the hydrated and dehydrated forms of 2 indicated a change, on comparison with the simulated diffractograph. The fluorescence properties of both these complexes, possessing tryptophan and bipy/phen, were investigated.     

Infinite chains constructed from flexible bis(benzimidazole)-based ligands

Two neutral ligands, L¹ · 2H₂O and L² · H₂O, and seven complexes, [Cu(pmb)₂(L¹)] (1), [Cu(pmb)₂(L²)] (2), [Cu(Ac)₂(L²)] · 4H₂O (3), [Cu(4-aba)₂(L²)] (4), [Ag(4-ts)(L¹)(H₂O)] (5), [Ag₂(epes)₂(L¹)] · 2H₂O (6), [Ag(1,5-nds)_0.5(L²)] · 0.5C₂H₅OH · H₂O (7) [where L¹ = 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole); L² = 1,1′-(1,4-butanediyl)bis(2-ethylbenzimidazole), pmb = p-methoxybenzoate anion; Ac = acetate anion; 4-aba = 4-aminobenzoate anion; 4-ts = p-toluenesulfonate anion; epes = N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonate) anion; 1,5-nds = 1,5-naphthalenedisulfonate anion], have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The L¹ and L² ligands in compounds 1–7 act as bridging ligands, linking metal ions into chain structures. The chains in compounds 3, 4 and 6 interlace with each other by hydrogen bonds to generate 3D supramolecular structures. In compound 5, π–π interactions between adjacent L¹ ligands hold the chains to a supramolecular layer. In compound 7, the sulfonate anions act as counterions in the framework. The thermal stabilities of 3, 6 and 7, and the luminescent properties for 5–7 in the solid states are also discussed.     

Synthesis,structural characterization and solvent effect of copper(II) complexes with a variational multidentate Salen-type ligand with bisoxime groups

Four new solvent-induced Cu(II) complexes with the chemical formulae [{Cu(HL)(CH₃OH)}₂Cu] · CH₃OH (1), [{(Cu(HL))₂(CH₃CH₂OH)₂}Cu] (2), [{CuL(H₂O)}₂Cu₂] · 2CH₃CH₂CH₂OH (3) and [{(Cu(HL))₂(CH₃CH₂CH₂CH₂OH)₂}Cu] (4), where H₄L = 6,6′-dihydroxy-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol, have been synthesized and characterized by elemental analyses, ¹H NMR, FT-IR, UV–Vis spectra, TG-DTA, molar conductances and X-ray crystallography. Complexes 1, 2 and 4 have an elongated square-pyramidal geometry with an unusually long bond from the penta-coordinated Cu(II) centres to the oxygen atoms of the apically coordinated solvent (methanol, ethanol or n-butanol) molecules for the terminal Cu(II) ions, and a square planar geometry distorted tetrahedrally for the central Cu(II) ion. In complex 3, the terminal Cu(II) ions have trigonal bipyramidal coordination geometries constituted by equatorial O₂N donor sites, with one oxygen atom from one of the coordinated water molecules and one nitrogen atom from a completely deprotonated L⁴⁻ ligand unit in the axial positions, and the central Cu(II) ions are in slightly tetrahedrally distorted square planar geometries constituted by four phenoxo oxygen donors from two completely deprotonated L⁴⁻ ligand units, and these form a tetrametal Cu–O–Cu–O–Cu–O–Cu–O eight-membered ring. These four complexes exhibit strong hydrogen bonding interactions in the solid state. Moreover, co-crystallizing n-propanol molecules link two other adjacent complex molecules into a self-assembled infinite 2D supramolecular structure via the intermolecular hydrogen bonds in complex 3.     

One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis,crystal structures and magnetic properties

Four new coordination polymers were obtained by employing polycarboxylato spacers and cationic copper(II) complexes as nodes: ^∞₂[Cu₃(trim)₂(NH₃)₆(H₂O)₃] (1); ^∞₁[Cu(tmen)(dhtp)] (2), ^∞₁[Cu(tmen)(hitp)(H₂O)] (3), ^∞₁[Cu(tmen)(nitp)] (4). (H₃trim = trimesic acid, H₂dhtp = 2,5-dihydroxy-terephthalic acid; H₂hitp = 5-hydroxy-isophthalic acid, H₂nitp = 5-nitro-isophthalic acid; tmen = N,N,N′,N′-tetramethyl-ethylenediamine). The crystal structures of the four compounds have been solved. Compound 1 consists of 2D coordination polymers with heart-shaped meshes, while compounds 2–4 contain infinite zigzag chains. The role of the hydrogen bond interactions in sustaining the supramolecular solid-state architectures in compounds 1 and 3 is discussed. The cryomagnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic interactions between the copper ions.     

Fe Spin crossover materials based on dissymmetrical N4 Schiff bases including 2-pyridyl and 2R-imidazol-4-yl rings: Synthesis,crystal structure and magnetic and Mössbauer properties

The synthesis and characterization of new symmetrical Fe^II complexes, [FeL^A(NCS)₂] (1), and [FeL^Bx(NCS)₂] (2–4), are reported (L^A is the tetradentate Schiff base N,N′-bis(1-pyridin-2-ylethylidene)-2,2-dimethylpropane-1,3-diamine, and L^Bx stands for the family of tetradentate Schiff bases N,N′-bis[(2-R-1H-imidazol-4-yl)methylene]-2,2-dimethylpropane-1,3-diamine, with: R = H for L^B1 in 2, R = Me for L^B2 in 3, and R = Ph for L^B3 in 4). Single-crystal X-ray structures have been determined for 1 (low-spin state at 293 K), 2 (high-spin (HS) state at 200 K), and 3 (HS state at 180 K). These complexes remain in the same spin-state over the whole temperature range [80–400 K]. The dissymmetrical tetradentate Schiff base ligands L^Cx, N-[(2-R₂-1H-imidazol-4-yl)methylene]-N′-(1-pyridin-2-ylethylidene)-2,2-R₁-propane-1,3-diamine (R₁ = H, Me; R₂ = H, Me, Ph), containing both pyridine and imidazole rings were obtained as their [FeL^Cx(NCS)₂] complexes, 5–10, through reaction of the isolated aminal type ligands 2-methyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = H, 5–7) or 2,5,5-trimethyl-2-pyridin-2-ylhexahydropyrimidine (R₁ = Me, 8–10) with imidazole-4-carboxaldehyde (R₂ = H: 5, 8), 2-methylimidazole-4-carboxaldehyde (R₂ = Me: 6, 9), and 2-phenyl-imidazole-4-carboxaldehyde (R₂ = Ph: 7, 10) in the presence of iron(II) thiocyanate. Together with the single-crystal X-ray structures of 7 and 9, variable-temperature magnetic susceptibility and Mössbauer studies of 5–10 showed that it is possible to tune the spin crossover properties in the [FeL^Cx(NCS)₂] series by changing the 2-imidazole and/or C2-propylene susbtituent of L^Cx.     

Dinuclear copper(II) complexes of a novel 3-(aminomethyl)naphthoquinone Mannich base: Synthesis,structural, magnetic and electrochemical studies

A novel versatile tridentate 3-(aminomethyl)naphthoquinone proligand, 3-[N-(2-pyridylmethyl)aminobenzyl]-2-hydroxy-1,4-naphthoquinone (HL), was obtained from the Mannich reaction of 2-hydroxy-1,4-naphthoquinone (Lawsone) with 2-aminomethylpyridine (amp) and benzaldehyde. The reactions of HL with CuCl₂·2H₂O yielded two novel dinuclear copper(II) complexes, [Cu(L)(H₂O)(μ-Cl)Cu(L)Cl] (1b), [CuCl(L)(μ-Cl)Cu(amp)Cl] (2) and a polymeric compound, [Cu(L)Cl)]_n (1a), whose relative yields were sensitive to temperature, reagents concentration and presence of base. The crystalline structures of 1b and 2 were determined by X-ray diffraction studies. The two copper atoms in complex 1b are connected by a single chloro bridge with a Cu?Cu separation of 4.1342(8) Å and Cu(1)–Cl(1)–Cu(2) angle of 109.31(4)°. In complex 2 the two copper atoms are held together by a chloro and a naphthalen-2-olate bridges [Cu(1)–Cl(2)–Cu(2) and Cu(1)–O(1)–Cu(2) angles being 83.31(3) and 109.70(9)°, respectively, and the Cu?Cu separation, 3.3476(9) Å]. As expected, variable-temperature magnetic susceptibility measurements of complex 1b showed weak antiferromagnetic intramolecular coupling between the copper(II) centers, with J = −5.7 cm⁻¹, and evidenced for complex 2 strong antiferromagnetic coupling, with J ∼ −120 cm⁻¹. Furthermore, the magnetic behaviour of compound 1a suggested an infinite 1D coordination polymeric structure in which the copper(II) centers are connected by Cl–Cu–Cl bridges. Solution data (UV–Vis spectroscopy and cyclic voltammetry) indicated structural changes of 2 and 1a in CH₃CN, and evidenced conversion of polymer 1a into dimer 1b.     

Controlled vinyl-addition-type polymerization of norbornene initiated by several cobalt complexes having substituted terpyridine ligands

A series of cobalt(II) complexes having terpyridine derivatives such as 2,2^′:6^′,2″-terpyridine (1), 4,4^′,4″-^tBu₃-2,2^′:6^′,2″-terpyridine (2), 5,5″-Me₂-2,2^′:6^′,2″-terpyridine (3), 6,6″-Me₂-2,2^′:6^′,2″-terpyridine (4) and 6,6″-(3,5-Me₂C₆H₃)₂-2,2^′:6^′,2″-terpyridine (5) was synthesized. The structures of 1, 3, and 4 were confirmed by X-ray crystallography. The coordination sphere around the cobalt center in 1 can be described as pseudo square pyramidal. On the other hand, complex 4 has pseudo trigonal bipyramidal structure. Upon activation with d-MAO (dried-methylaluminoxane), these complexes showed high activities for the polymerization of norbornene (NBE). In particular, polymerization of NBE with 4/d-MAO system at room temperature resulted in quantitative yield within several hours to give the polymers with relatively narrow molecular weight distributions and controlled molecular weight. The polymerizations of NBE with these cobalt catalyst systems proceeded in vinyl addition polymerization, which was confirmed by ¹H NMR spectra of the resulting polymers.     

W/Cu(Ag)/S complexes containing bridging diphosphine ligands: Synthesis,structures and optical properties

The substitution reactions of [Et₄N]₂[WOS₃MCN] (M = Cu, Ag) with dppe (dppe = 1,2-bis(diphenylphosphino) ethane) in DMF afforded a tetranuclear cluster [Et₄N]₂[WOS₃Cu(dppe)]₂ · H₂O (1) and a polymer [WEE′S₂Ag(dppe)]₂ · CH₃CN (3) (E = 0.636S + 0.364O, E′ = 0.581O + 0.419S), respectively. Treatment of 1 with AgI at elevated temperature yielded polymeric complex [WS₄Cu₂(dppe)₂]_n (2). X-ray single crystal structural analyses revealed that in both 1 and 2, the W/Cu/S cluster units are linked by two dppe ligands to form a 10-membered [–Cu–P–C–C–P–]₂ ring. In the polymeric structure of 2, the W and Cu atoms form a helical chain whereas in 3 the cluster units (WEE′S₂Ag) are bridged by dppe ligands affording a zig-zag chain structure. The optical absorption spectra and the solid-state photoluminescent properties of the title complexes are also studied.     

Dinuclear copper(II) perchlorate complexes with 6-(benzylamino)purine derivatives: Synthesis,X-ray structure,magnetism and antiradical activity

The reactions of Cu(ClO₄)₂·6H₂O with 6-(benzylamino)purine derivatives in a stoichiometric 1:2 metal-to-ligand ratio led to the formation of penta-coordinated dinuclear complexes of the formula [Cu₂(μ-L^1–8)₄(ClO₄)₂](ClO₄)₂·nsolv, where L¹ = 6-(2-fluorobenzylamino)purine (complex 1), L² = 6-(3-fluorobenzylamino)purine (2), L³ = 6-(4-fluorobenzylamino)purine (3), L⁴ = 6-(2-chlorobenzylamino)purine (4), L⁵ = 6-(3-chlorobenzylamino)purine (5), L⁶ = 6-(4-chlorobenzylamino)purine (6), L⁷ = 6-(3-methoxybenzylamino)purine (7) and L⁸ = 6-(4-methoxybenzylamino)purine (8); n = 0–4 and solv = H₂O, EtOH or MeOH. All the complexes have been fully characterized by elemental analysis, FTIR, UV–Vis and EPR spectroscopy, and by magnetic and conductivity measurements. Variable temperature (80–300 K) magnetic susceptibility data of 1–8 showed the presence of a strong antiferromagnetic exchange interaction between two Cu(II) (S = 1/2) atoms with J ranging from −150.0(1) to −160.3(2) cm⁻¹. The compound 6·4EtOH·H₂O was structurally characterized by single crystal X-ray analysis. The Cu?Cu separation has been found to be 2.9092(8) Å. The antiradical activity of the prepared compounds was tested by in vitro SOD-mimic assay with IC₅₀ in the range 8.67–41.45 μM. The results of an in vivo antidiabetic activity assay were inconclusive and the glycaemia in pre-treated animals did not differ significantly from the positive control.     

Photoactive building blocks for coordination complexes: Gilding 2,2′:6′,2″-terpyridine

The alkyne unit of 4′-ethynyl-2,2′:6′,2″-terpyridine has been functionalized with Ph₃PAu, (2-tolyl)₃PAu or Au(dppe)Au units to produce compounds 1-3, respectively. These derivatives have been characterized by electrospray mass spectrometry, solution ¹H and ¹³C NMR, UV-Vis and emission spectroscopies, and single crystal X-ray diffraction. In the solid state, molecules of 1 or 2 pack with separated domains of tpy and R₃PAu units; the tpy units in 2 (but not 1) exhibit face-to-face π-stacking. Compound 3 crystallizes as 2(3)^.CHCl₃, and the folded conformation of the dppe backbone results in a short (2.9470(8) Å) aurophilic interaction. Folded molecule 3 captures CHCl₃, preventing intramolecular face-to-face π-interactions between the tpy units. In CH₂Cl₂ solution, 1-3 are emissive when excited between 230 and 300 nm, but over minutes when λ_ex = 230 nm, the emission bands decay as the compounds photodegrade.     

Oxidative and hydrolytic DNA cleavage by Cu(II) complexes of salicylidene tyrosine schiff base and 1,10 phenanthroline/bipyridine

Ternary Cu(II) complexes [Cu(II)(saltyr)(B)] (1,2), (saltyr = salicylidene tyrosine, B = 1,10 phenanthroline (1) or 2,2′ bipyridine (2)) were synthesized and characterized by various techniques. The complexes exhibit square pyramidal (CuN₃O₂) geometry. CT-DNA binding studies revealed that the complexes show good binding propensity (K_b = 3.47 × 10⁴ M⁻¹ and 3.01 × 10⁴ M⁻¹ for 1 and 2, respectively). The role of these complexes in the oxidative and hydrolytic DNA cleavage was studied. The catalytic ability of 1 and 2 follows the order: 1 > 2. The rate constants for the hydrolysis of phosphodiester bond were determined as 2.80 h⁻¹ and 2.11 h⁻¹ for 1 and 2, respectively. It amounts to (0.58-0.77) × 10⁸ fold rate enhancement compared to non-catalyzed DNA cleavage, which is significant.