Unusual photophysical switching in a Ru(II) diimine DNA probe caused by amide functionalisation

Whereas the complex [Ru(phen)2Medpq]2+(phen=1,10-phenanthroline; Medpq=2-methyldipyrido[3,2-f:2',3'-h]-quinoxaline) is luminescent in both aqueous and nonaqueous solutions, [Ru(phen)2dpqa]2+(2-pentylamidodipyrido[3,2-f:2',3'-h]-quinoxaline) does not emit in water but does so strongly in organic solvents or when bound to DNA--suggesting its use as a photochemical and photophysical probe for nucleic acids.     

Synthesis and characterization of ruthenium(II) molecular assemblies for photosensitization of nanocrystalline TiO2: utilization of hydroxyl grafting mode

New Ru polypyridine complexes [(bpy)2Ru(L)]2+, where bpy = 2,2'-bipyridine and L = dipyrido[3,2-a:2',3'-c]-phenazine-2-carboxylic acid (dppzc), dipyrido[3,2-f:2',3'-h]quinoxaline-2,3-dicarboxylic acid (dpq(COOH)2), 3-hydroxydipyrido[3,2-f:2',3'-h]quinoxaline-2-carboxylic acid (dpq(OHCOOH)), 2,3-dihydroxydipyrido[3,2-f:2',3'-h]quinoxaline (dpq(OH)2), and [(L')Ru(dppzc)2]2+, where L' = bpy and 1,10-phenanthroline (phen), have been synthesized, characterized, and anchored to nanocrystalline TiO2 electrodes for light to electrical energy conversion in regenerative photoelectrochemical cells with I-/I2 acetonitrile electrolyte. These sensitizers have intense metal-to-ligand charge-transfer (MLCT) bands centered at approximately 450 nm. The effect of pH on the absorption and emission spectra of these complexes consisting of protonatable ligands has been investigated in water by spectrophotometric titration. The excited-state pKa values are more basic than the ground-state ones, except the pKa2 and pKa2* in [(bpy)2Ru(dpq(OH)2)]2+, which are equal, suggesting the localization of the lowest-energy MLCT on heteroaromatic bridging ligands, dppzc and dpq. Incident photon-to-current conversion efficiency (IPCE) is sensitive to the structural changes that resulted from introducing different functional groups, used for grafting.     

Design of rhenium(I) polypyridine biotin complexes as a new class of luminescent probes for avidin

This paper describes the design of a series of luminescent rhenium(I) polypyridine biotin complexes containing different spacer-arms, [Re(N-N)(CO)3 (py-4-CH2-NH-biotin)](PF6) (py-4-CH2-NH-biotin = 4-(biotinamidomethyl)pyridine; N-N = 1,10-phenanthroline, phen (1a), 3,4,7,8-tetramethyl-1,10-phenanthroline, Me4-phen (2a), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, Me2-Ph2-phen (3a), dipyrido[3,2-f:2',3'-h]quinoxaline, dpq (4a)), [Re(N-N)(CO)3 (py-3-CO-NH-en-NH-biotin)](PF6) (py-3-CO-NH-en-NH-biotin = 3-(N-((2-biotinamido)ethyl)amido)pyridine; N-N = phen (1b), Me4-phen (2b), Me2-Ph2-phen (3b), dpq (4b)), and [Re(N-N)(CO)3 (py-4-CH2-NH-cap-NH-biotin)](PF6) (py-4-CH2-NH-cap-NH-biotin = 4-(N-((6-biotinamido)hexanoyl)aminomethyl)pyridine; N-N = phen (1c), Me4-phen (2c), Me2-Ph(2)-phen (3c), dpq (4c)). Upon irradiation, all of the rhenium(I)-biotin complexes exhibited intense and long-lived triplet metal-to-ligand charge-transfer (3MLCT) (d pi(Re) --> pi* (diimine)) emission in fluid solutions at 298 K. The interactions of these biotin-containing complexes with avidin have been studied by 4'-hydroxyazobenzene-2-carboxylic acid (HABA) assays, emission titrations, and competitive association and dissociation assays. On the basis of the results of these experiments, homogeneous assays for biotin and avidin have been designed.     

Nucleic acid intercalators and avidin probes derived from luminescent cyclometalated iridium(III)-dipyridoquinoxaline and -dipyridophenazine complexes

Six luminescent cyclometalated iridium(III)-dipyridoquinoxaline and -dipyridophenazine complexes [Ir(ppy)2(N-N)](PF6) (Hppy = 2-phenylpyridine; N-N = dipyrido[3,2-f:2',3'-h]quinoxaline, dpq (1); 2-n-butylamidodipyrido[3,2-f:2',3'-h]quinoxaline, dpqa (2); 2-((2-biotinamido)ethyl)amidodipyrido[3,2-f:2',3'-h]quinoxaline, dpqB (3); dipyrido[3,2-a:2',3'-c]phenazine, dppz (4); benzo[i]dipyrido[3,2-a:2',3'-c]phenazine, dppn (5); 11-((2-biotinamido)ethyl)amidodipyrido[3,2-a:2',3'-c]phenazine, dppzB (6)) have been designed as luminescent intercalators for DNA and probes for avidin. The structure of complex 4 has been studied by X-ray crystallography. The photophysical and electrochemical properties of the complexes have also been investigated. The binding of these complexes to double-stranded calf thymus DNA and synthetic double-stranded oligonucleotides poly(dA) x poly(dT) and poly(dG) x poly(dC) has been investigated by spectroscopic titrations. The interactions between the two biotin-containing complexes and avidin have been studied by 4'-hydroxyazobenzene-2-carboxylic acid (HABA) assays and emission titrations.     

Hydrothermal Syntheses and Crystal Structures of Two Metal-organic Complexes with 2,3-Pyridinedicarboxylic Acid and 2-Methyl-dipyrido[3,2-f：2＇,3＇-h]quinoxaline Ligands

Two unusual one-dimensional(1-D) compounds,viz.[Co(Medpq)(QUI)·H2O]2n· 2.4nH2O 1 and [Cd(Medpq)(QUI)·H2O]n·nH2O 2,were synthesized by the combination of two different metallic salts and organic ligands,namely 2,3-pyridinedicarboxylic acid(H2QUI) and 2-methyldipyrido[3,2-f:2',3'-h]quinoxaline(Medpq) ligand.The compounds were characterized by elemental analyses,TG,fluorescent emission and single-crystal X-ray diffraction analyses.     

Dual molecular light switches for pH and DNA based on a novel Ru(II) complex. A non-intercalating Ru(II) complex for DNA molecular light switch

A new Ru(II) complex of [Ru(phen)(2)(Hcdpq)](ClO(4))(2) {phen = 1,10-phenanthroline, Hcdpq = 2-carboxyldipyrido[3,2-f:2',3'-h]quinoxaline} was synthesized and characterized. The spectrophotometric pH and calf thymus DNA (ct-DNA) titrations showed that the complex acted as a dual molecular light switch for pH and ct-DNA with emission enhancement factors of 17 and 26, respectively. It was shown to be capable of distinguishing ct-DNA from yeast RNA with this binding selectivity being superior to two well-known DNA molecular light switches of [Ru(bpy)(2)(dppz)](2+) {bpy =2,2'-bipyridine, and dppz = dipyrido-[3,2-a:2',3'-c]phenazine}and ethidium bromide. The complex bond to ct-DNA probably in groove mode with a binding constant of (4.67 ± 0.06) × 10(3) M(-1) in 5 mM Tris-HCl, 50 mM NaCl (pH = 7.10) buffer solution, as evidenced by UV-visible absorption and luminescence titrations, the dependence of DNA binding constants on NaCl concentrations, DNA competitive binding with ethidium bromide, and emission lifetime and viscosity measurements. To get insight into the light-switch mechanism, theoretical calculations were also performed by applying density functional theory (DFT) and time-dependent DFT.     

配合物[Ni(Pht)(Medpq)(H2O)3]n的水热合成、表征及自然键轨道(NBO)分析

采用水热法合成了一种新型金属配合物[Ni(Pht)(Medpq)(H2O)3]n(1)(Pht=phthalic acid,Medpq=2-methyldipyrido[3,2-f∶2′,3′-h]quinoxaline),并对其进行了元素分析、红外光谱、热重表征、X射线单晶衍射测定和理论计算。在晶体中,Ni(Ⅱ)与来自于Medpq分子上的2个氮原子,邻苯二甲酸上的1个氧原子及来自于3个不同的配位水分子上的3个氧原子配位,形成畸变的八面体构型。整个晶体由Pht-Ni-Medpq单元组成零维结构。应用Guassian03W程序,在HF/LANL2DZ水平上对标题化合物的自然键轨道(NBO)进行了分析,结果表明Ni(Ⅱ)与配位原子间的价键类型都属于共价键范畴。     

Mixed ligand ruthenium(II) complexes of bis(pyrid-2-yl)-/bis(benzimidazol-2-yl)-dithioether and diimines: study of non-covalent DNA binding and cytotoxicity

A series of mixed ligand ruthenium(II) complexes [Ru(pdto)(diimine)](ClO4)2/(PF6)2 1-3 and [Ru(bbdo)(diimine)](ClO4), 4-6, where pdto is 1,8-bis(pyrid-2-yl)-3,6-dithiooctane, bbdo is 1,8-bis(benzimidazol-2-yl)-3,6-dithiooctane and diimine is 1,10-phenanthroline (phen), dipyrido-[3,2-d:2',3'-f]-quinoxaline (dpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz), have been isolated and characterised by analytical and spectral methods. The complexes [Ru(pdto)(phen)](PF6)2 la, [Ru(pdto)(dpq)(Cl](PF6) 2a, [Ru(bbdo)(phen)](PF6)2 4a and [Ru(bbdo)(dpq)](ClO4)2 5 have been structurally characterized and their coordination geometries around ruthenium(II) are described as distorted octahedral. In la, 4a and 5 the two thioether sulfur and two py/bzim nitrogen atoms of the tetradentate pdto/bbdo ligand are folded around Ru(II) to give predominantly a "cis-alpha" configuration. (I)H NMR spectral data of the complexes support this configuration in solution. In [Ru(pdto)(dpq)Cl](PF6) 2a with a distorted octahedral coordination geometry, one of the two py nitrogens of pdto is not coordinated. The DNA binding constants (Kb: 2, 2.00 +/- 0.02 x 10(4) M(-1), s = 1.0; 3, 3.00 +/- 0.01 x 10(6) M(-1), s = 1.3) determined by absorption spectral titrations of the complexes with CT DNA reveal that 3 interacts with DNA more tightly than 2 through partial intercalation of the extended planar ring of coordinated dppz with the DNA base stack. The DNA binding affinities of the complexes increase with increase in the number of planar aromatic rings in the co-ligand, and on replacing both the py moieties in pdto complexes (1-3) by bzim moieties to give bbdo complexes (4-6). Upon interaction with CT DNA the complexes 1, 2, 5 and 6 show a decrease in anodic current in the cyclic voltammograms. On the other hand, interestingly, 3 and 4 show an increase in anodic current suggesting their involvement in electrocatalytic guanine oxidation. Interestingly, of all the complexes, only 6 alters the superhelicity of DNA upon binding with supercoiled pBR322 DNA. The cytotoxicities of the dppz complexes 3 and 6, which avidly bind to DNA, have been examined by screening them against cell lines of different cancer origins. It is noteworthy that 6 exhibits selectivity with higher cytotoxicity against the melanoma cancer cell line (A375) than other cell lines, potency approximately twice that of cisplatin and toxicity to normal cells 3 and 90 times less than cisplatin and adriamycin respectively.     

Asymmetric cooperativity in tandem hybridization of enantiomeric metal complex-tethered short fluorescent DNA probes

The complex [Ru(phen)(2)(dppz)](2+)(phen = 1,10-phenanthroline, dppz = dipyrido[3,2-aratio2',3'-c]phenazine) was attached to the 5' end of a short oligonucleotide to form conjugates, the Delta-isomer of which showed a high cooperativity during the recognition of the repetitive sequence, while the Lambda-isomer did not.     

Interaction of rac-[Cu(diimine)3]2+ and rac-[Zn(diimine)3]2+ complexes with CT DNA: effect of fluxional Cu(II) geometry on DNA binding, ligand-promoted exciton coupling and prominent DNA cleavage

The complexes [Cu(phen)(3)](ClO(4))(2) 1, [Cu(5,6-dmp)(3)](ClO(4))(2) 2, [Cu(dpq)(3)](ClO(4))(2) 3, [Zn(phen)(3)](ClO(4))(2) 4, [Zn(5,6-dmp)(3)](ClO(4))(2) 5 and [Zn(dpq)(3)](ClO(4))(2) 6, where phen = 1,10-phenanthroline, 5,6-dmp = 5,6-dimethyl-1,10-phenanthroline and dpq = dipyrido[3,2-d:2',3'-f]quinoxaline, have been isolated, characterized and their interaction with calf thymus DNA studied by using a host of physical methods. The X-ray crystal structures of rac-[Cu(5,6-dmp)(3)](ClO(4))(2) and rac-[Zn(5,6-dmp)(3)](ClO(4))(2) have been determined. While 2 possesses a regular elongated octahedral coordination geometry (REO), 5 possesses a distorted octahedral geometry. Absorption spectral titrations of the Cu(II) complexes with CT DNA reveal that the red-shift (12 nm) and DNA binding affinity of 3 (K(b), 7.5 x 10(4) M(-1)) are higher than those of 1 (red-shift, 6 nm; K(b), 9.6 x 10(3) M(-1)) indicating that the partial insertion of the extended phen ring of dpq ligand in between the DNA base pairs is deeper than that of phen ring. Also, 2 with a fluxional Cu(II) geometry interacts with DNA (K(b), 3.8 x 10(4) M(-1)) more strongly than 1 suggesting that the hydrophobic forces of interaction of 5,6 methyl groups on the phen ring is more pronounced than the partial intercalation of phen ring in the latter with a static geometry. The DNA binding affinity of 1 is lower than that of its Zn(ii) analogue 4, and, interestingly, the DNA binding affinity 2 of with a fluxional geometry is higher than that of its Zn(II) analogue 5 with a spherical geometry. It is remarkable that upon binding to DNA 3 shows an increase in viscosity higher than that the intercalator EthBr does, which is consistent with the above DNA binding affinities. The CD spectra show only one induced CD band on the characteristic positive band of CT DNA upon interaction with the phen (1,4) and dpq (3,6) complexes. In contrast, the 5,6-dmp complexes 2 and 5 bound to CT DNA show exciton-coupled biphasic CD signals with 2 showing CD signals more intense than 5. The Delta-enantiomer of rac-[Cu(5,6-dmp)(3)](2+) 2 binds specifically to the right-handed B-form of CT DNA at lower ionic strength (0.05 M NaCl) while the Lambda-enantiomer binds specifically to the left-handed Z-form of CT DNA generated by treating the B-form with 5 M NaCl. The complex 2 is stabilized in the higher oxidation state of Cu(II) more than its phen analogue 1 upon binding to DNA suggesting the involvement of electrostatic forces in DNA interaction of the former. In contrast, 3 bound to DNA is stabilized as Cu(I) rather than the Cu(II) oxidation state due to partial intercalative interaction of the dpq ligand. The efficiencies of the complexes to oxidatively cleave pUC19 DNA vary in the order, 3> 1 > 2 with 3 effecting 100% cleavage even at 10 microM complex concentration. However, interestingly, this order is reversed when the DNA cleavage is performed using H(2)O(2) as an activator and the highest cleavage efficiency of 2 is ascribed to its electrostatic interaction with the exterior phosphates of DNA.     

Role of electronic structure on DNA light-switch behavior of Ru(II) intercalators

A series of ruthenium(II) complexes possessing ligands with an extended pi system were synthesized and characterized. The complexes are derived from [Ru(bpy)3](2+) (1, bpy = 2,2'-bipyridine) and include [Ru(bpy)2(tpphz)](2+) (2, tpphz = tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]phenazine), [Ru(bpy)2(dppx)](2+) (3, dppx = 7,8-dimethyldipyrido[3,2-a:2',3'-c]phenazine), [Ru(bpy)2(dppm2)](2+) (4, dppm2 = 6-methyldipyrido[3,2-a:2',3'-c]phenazine), and [Ru(bpy)2(dppp2)](2+) (5, dppp2 = pyrido[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline). The excited-state properties of these complexes, including their DNA "light-switch" behavior, were compared to those of [Ru(bpy)2(dppz)](2+) (6, dppz = dipyrido[3,2-a:2',3'-c]phenazine). Whereas 2, 3, and 4 can be classified as DNA light-switch complexes, 5 exhibits negligible luminescence enhancement in the presence of DNA. Because relative viscosity experiments show that 2-6 bind to DNA by intercalation, their electronic absorption and emission spectra, electrochemistry, and temperature dependence of the luminescence were used to explain the observed differences. The small energy gap between the lowest-lying dark excited state and the bright state in 2-4 and 6 is related to the ability of these complexes to exhibit DNA light-switch behavior, whereas the large energy gap in 5 precludes the emission enhancement in the presence of DNA. The effect of the energy gap among low-lying states on the photophysical properties of 1-6 is discussed. In addition, DFT and TD-DFT calculations support the conclusions from the experiments.     

Double-strand DNA cleavage from photodecarboxylation of (micro-oxo)diiron(III) L-histidine complex in visible light

The oxo-bridged diiron(III) complex [{Fe(L-his)(dpq)}(2)(micro-O)](2+) having L-histidine (L-his) and dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) bound to Fe(III) exemplifies an iron-based model photonuclease that shows visible light-induced DNA double-strand cleavage in a photodecarboxylation pathway and models iron-bleomycin activity.     

Mono- and dinuclear ruthenium(II) 1,6,7,12-tetraazaperylene complexes

We report the synthesis of free 1,6,7,12-tetraazaperylene (tape). Tape was obtained from 1,1'-bis-2,7-naphthyridine by potassium promoted cyclization followed by oxidation with air. Mono- and dinuclear ruthenium(II) 1,6,7,12-tetraazaperylene complexes of the general formulas [Ru(L-L)(2)(tape)](PF(6))(2), [1](PF(6))(2)-[5](PF(6))(2), and [{Ru(L-L)(2)}(2)(μ-tape)](PF(6))(4), [6](PF(6))(4)-[10](PF(6))(4), with{L-L = phen, bpy, dmbpy (4,4'-dimethyl-2,2'-bipyridine), dtbbpy (4,4'-ditertbutyl-2,2'-bipyridine) and tmbpy (4,4'5,5'-tetramethyl-2,2'-bipyridine)}, respectively, were synthesized. The X-ray structures of tape·2CHCl(3) and the mononuclear complexes [Ru(bpy)(2)(tape)](PF(6))(2)·0.5CH(3)CN·0.5toluene, [Ru(dmbpy)(2)(tape)](PF(6))(2)·2toluene and [Ru(dtbbpy)(2)(tape)](PF(6))(2)·3acetone·0.5H(2)O were solved. The UV-vis absorption spectra and the electrochemical behavior of the ruthenium(ii) tape complexes were explored and compared with the data of the analogous dibenzoeilatin (dbneil), 2,2'-bipyrimidine (bpym) and tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]phenazin (tpphz) species.     

Trinuclear ruthenium dendrons based on bridging PHEHAT and TPAC ligands

Novel polynuclear compounds, the trinuclear precursor complex cis-{[(phen)(2)Ru(PHEHAT)](2)Ru(CH(3)CN)(2)}(6+) 4 and the trinuclear TPAC (tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]acridine) complex {[(phen)(2)Ru(PHEHAT)](2)Ru(TPAC)}(6+) 5 have been prepared. Their electrochemistry and photophysics indicate that the (3)MLCT (metal to ligand charge transfer) emissions involve the external {Ru(PHEHAT)} moieties for both complexes and there is no spectro-electrochemical correlation. The trinuclear dendron with the TPAC ligand represents a key compound for future constructions of much larger species thanks to the TPAC that could bridge another polynuclear precursor. For decreasing the length of preparation of these compounds, microwave assisted syntheses have been tested and used not only for the targeted complexes but also for the precursors ((phen)(2)RuCl(2), {(phen)(2)Ru(phendione)}(2+), {(phen)(2)Ru(PHEHAT)}(2+) (PHEHAT = 1,10-phenanthrolino[5,6-b]1,4,5,8,9,12-hexaazatriphenylene), (DMSO)(4)RuCl(2)), and for the bridging TPAC ligand itself. The microwave method allows a drastic decrease of the preparation times, especially in the case of the TPAC, from 8 days to 60 min.     

Electrochemiluminescent peptide nucleic acid-like monomers containing Ru(II)-dipyridoquinoxaline and Ru(II)-dipyridophenazine complexes

A series of Ru(II)-peptide nucleic acid (PNA)-like monomers, [Ru(bpy)(2)(dpq-L-PNA-OH)](2+) (M1), [Ru(phen)(2)(dpq-L-PNA-OH)](2+) (M2), [Ru(bpy)(2)(dppz-L-PNA-OH)](2+) (M3), and [Ru(phen)(2)(dppz-L-PNA-OH)](2+) (M4) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, dpq-L-PNA-OH = 2-(N-(2-(((9H-fluoren-9-yl)methoxy)carbonylamino)ethyl)-6-(dipyrido[3,2-a:2',3'-c]phenazine-11-carboxamido)hexanamido)acetic acid, dppz-L-PNA-OH = 2-(N-(2-(((9H-fluoren-9-yl) methoxy)carbonylamino)ethyl)-6-(dipyrido[3,2-f:2',3'-h]quinoxaline-2-carboxamido)acetic acid) have been synthesized and characterized by IR and (1)H NMR spectroscopy, mass spectrometry, and elemental analysis. As is typical for Ru(II)-tris(diimine) complexes, acetonitrile solutions of these complexes (M1-M4) show MLCT transitions in the 443-455 nm region and emission maxima at 618, 613, 658, and 660 nm, respectively, upon photoexcitation at 450 nm. Changes in the ligand environment around the Ru(II) center are reflected in the luminescence and electrochemical response obtained from these monomers. The emission intensity and quantum yield for M1 and M2 were found to be higher than for M3 and M4. Electrochemical studies in acetonitrile show the Ru(II)-PNA monomers to undergo a one-electron redox process associated with Ru(II) to Ru(III) oxidation. A positive shift was observed in the reversible redox potentials for M1-M4 (962, 951, 936, and 938 mV, respectively, vs Fc(0/+) (Fc = ferrocene)) in comparison with [Ru(bpy)(3)](2+) (888 mV vs Fc(0/+)). The ability of the Ru(II)-PNA monomers to generate electrochemiluminescence (ECL) was assessed in acetonitrile solutions containing tripropylamine (TPA) as a coreactant. Intense ECL signals were observed with emission maxima for M1-M4 at 622, 616, 673, and 675 nm, respectively. At an applied potential sufficiently positive to oxidize the ruthenium center, the integrated intensity for ECL from the PNA monomers was found to vary in the order M1 (62%) > M3 (60%) > M4 (46%) > M2 (44%) with respect to [Ru(bpy)(3)](2+) (100%). These findings indicate that such Ru(II)-PNA bioconjugates could be investigated as multimodal labels for biosensing applications.     

DNA interaction of platinum(II) complexes with 1,10-phenanthroline and extended phenanthrolines

The interaction with DNA of the platinum(II) square planar complexes [Pt(N-N)(py)(2)](2+) (N-N = 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), dipyrido[3,2-a:2',3'-c]phenazine (dppz), benzodipyrido[b:3,2-h:2'3'-f]phenazine (bdppz)) has been investigated by means of absorption, circular and linear dichroism spectroscopy, DNA melting, and viscosity. In the presence of excess [DNA] all the complexes intercalate to the double helix. For those with the most extended phenanthrolines the binding mode depends on the [DNA]/[complex] ratio (q); at low q values the substances bind externally to DNA probably self-aggregating along the double helix. When the DNA concentration is large enough, the aggregate breaks up and the complex intercalates within the nucleobases. The complexes self-aggregate, without added DNA, in the presence of a large salt concentration.     

由邻苯二甲酸和Medpq配体构筑的锌的配合物的水热合成及晶体测定

A metal-organic coordination polymer [Zn(Pht)(Medpq)]_n (Pht=phthalic acid, Medpq=2-methyldipyrido[3,2-f:2′,3′-h]quinoxaline) (1) has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG and X-ray single-crystal structure analysis. Title complex crystallizes in the monoclinic system, space group Cc, with a=1.027 4(4) nm, b=2.955 7(11) nm, c=0.685 2(3) nm, β=112.941°, V=1.916 3(13) nm³, C₂₃H₁₄N₄O₄Zn, M_r=475.75, D_c=1.649 g·cm^-3, μ(Mo Kα)=1.324 mm^-1, F(000)=968, Z=4, the final R=0.038 8 and wR=0.071 7 for 2 697 observed reflections (I>2σ(I)). In the crystal structure, the Zinc atom is six-coordinated with four carboxylate oxygen atoms from two different carboxylate groups and two nitrogen atoms from Medpq ligand, showing a slightly distorted octahedral geometry. Furthermore, it exhibits a one-dimensional structure with Pht-Zn-Medpq as building units. CCDC: 716600.     

Ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn): preparation,crystal structures,and electrochemical and spectroscopic properties of [Ru(bpy or phen)(3)(-)(n)(Me(2)Pqn)(n)](PF(6))(2) (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; n = 1, 2, or 3)

Several new ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn) were synthesized, and their structures and electrochemical/spectroscopic properties have been investigated. In addition to the mono(Me(2)Pqn) complex [Ru(bpy or phen)(2)(Me(2)Pqn)](PF(6))(2) (1 or 1'; bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline), the geometrical isomers trans(P)- and C(1)-[Ru(bpy)(Me(2)Pqn)(2)](PF(6))(2) (tP-2 and C(1)-2) and mer- and fac-[Ru(Me(2)Pqn)(3)](PF(6))(2) (m-3 and f-3) were also selectively synthesized and isolated. It was found that complexes tP-2 and m-3 were converted quantitatively to the corresponding C(1)-2 and f-3 isomers, respectively, by irradiation of light corresponding to the MLCT transition energy. The strong trans influence of the Me(2)P- donor group of Me(2)Pqn was confirmed by the X-ray structural analyses for 1, tP-2, m-3, and f-3. Cyclic voltammetry of a series of complexes, [Ru(bpy)(3)](PF(6))(2), 1, C(1)-2, and f-3, exhibited a reversible one-electron oxidation wave and two or three one-electron reduction waves. The oxidation potentials of the complexes gave a large positive shift with increasing number of coordinated Me(2)Pqn molecules, indicating a larger pi-acceptability of the Me(2)P- group compared with bpy or qn. Complex f-3 in EtOH/MeOH (4:1) glass at 77 K exhibited an intense long-lived (tau = 920 microseconds) emission arising from the quinoline-based (3)(pi-pi) excited state. In contrast, the mixed-ligand complexes 1, 1', and C(1)-2 showed a characteristic dual emission, giving a double-exponential emission decay, and the dual emission originates from both the bpy-based (3)MLCT and the quinoline-based (3)(pi-pi) emitting states.     

由间苯二甲酸和Medpq配体构筑的一种新型零维铜(Ⅰ)的配合物的水热合成及晶体结构测定

A metal-organic Complex [Cu₂(ipt)(Medpq)₂]_n (ipt=isophthalic acid, Medpq=2-methyldipyrido[3,2-f:2′,3′-h]quinoxaline) 1 has been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. Title compound crystallizes in the monoclinic system, space group C2/c, with a=2.389 2(6) nm, b=0.709 60(18) nm, c=1.922 2(5) nm, β=108.655(3), V=3.087 8(14) nm³, C₃₈H₂₄Cu₂N₈O₄, M_r=783.73, D_c=1.686 g·cm^-3, Z=4, the final R=0.055 4 and wR=0.128 5. In the crystal structure, the copper atom is three-coordinated with one carboxylate oxygen atom from carboxylate groups and two nitrogen atoms from Medpq ligand, showing a slightly distorted triangle geometry. Furthermore, it exhibits a zero-dimensional structure with ipt-Cu- medpq as building units. CCDC: 747544.     

Marked differences in light-switch behavior of Ru(II) complexes possessing a tridentate DNA intercalating ligand

The tridentate ligand 3-(pyrid-2'-yl)dipyrido[3,2-a:2',3'-c]phenazine (pydppz) has been prepared in two steps by elaboration of 2-(pyrid-2'-yl)-1,10-phenanthroline. Both homoleptic [Ru(pydppz)(2)](2+) and heteroleptic [Ru(tpy)(pydppz)](2+) (tpy = 2,2';6',2' '-terpyridine) complexes have been prepared and characterized by (1)H NMR. The absorption and emission spectra are consistent with low-lying MLCT excited states, which are typical of Ru(II) complexes. Femtosecond transient absorption measurements show that that the (3)MLCT excited state of the heteroleptic complex [Ru(tpy)(pydppz)](2+) (tau approximately 5 ns) is longer-lived than that of the homoleptic complex [Ru(pydppz)(2)](2+) (tau = 2.4 ns) and that these lifetimes are significantly longer than that of the (3)MLCT state of the parent complex [Ru(tpy)(2)](2+) (tau = 120 ps). These differences are explained by the lower-energy (3)MLCT excited state present in [Ru(tpy)(pydppz)](2+) and [Ru(pydppz)(2)](2+) compared to [Ru(tpy)(2)](2+), resulting in less deactivation of the former through the ligand-field state(s). DFT and TDDFT calculations are consistent with this explanation. [Ru(tpy)(pydppz)](2+) and [Ru(pydppz)(2)](2+) bind to DNA through the intercalation of the pydppz ligand; however, only the heteroleptic complex exhibits luminescence enhancement in the presence of DNA. The difference in the photophysical behavior of the complexes is explained by the inability of [Ru(pydppz)(2)](2+) to intercalate both pydppz ligands, such that one pydppz always remains exposed to the solvent. DNA photocleavage is observed for [Ru(tpy)(pydppz)](2+) in air, but not for [Ru(pydppz)(2)](2+). The DNA damage likely proceeds through the production of small amounts of (1)O(2) by the longer-lived complex. Although both complexes possess the intercalating pydppz ligand, they exhibit different photophysical properties in the presence of DNA.