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.     

Complexes of functionalized dipyrido[3,2-a:2',3'-c]-phenazine: a synthetic, spectroscopic, structural, and density functional theory study

The ligands 11-bromodipyrido[3,2-a:2',3'-c]phenazine and ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate have been prepared and coordinated to ruthenium(II), rhenium(I), and copper(I) metal centers. The electronic effects of substitution of dipyrido[2,3-a:3',2'-c]phenazine (dppz) have been investigated by spectroscopy and electrochemistry, and some photophysical properties have been studied. The crystal structures of [Re(L)(CO)(3)Cl] (L = ethyl dipyrido[3,2-a:2',3'-c]phenazine-11-carboxylate or 11-bromodipyrido[3,2-a:2',3'-c]phenazine) are presented. Density functional theory calculations on the complexes show only small deviations in bond lengths and angles (most bonds within 0.02 Angstroms, most angles within 2 degrees) from the crystallographic data. Furthermore, the vibrational spectra of the strongest Raman and IR bands are predicted to within an average 6 cm(-1) for the complexes [Re(L)(CO)(3)Cl] and [Cu(L)(triphenylphosphine)(2)]BF(4) (in the 1000-1700 cm(-1) region). Spectroscopic and electrochemical evidence suggest that reduction of the complex causes structural changes across the entire dppz ligand. This is unusual as dppz-based ligands typically have electrochemical properties that suggest charge localization with reduction on the phenazine portion of the ligand. The excited-state lifetimes of the complexes have been measured, and they range from ca. 200 ns for the [Ru(L)(2,2'-bipyridine)(2)](PF(6))(2) complexes to over 2 mus for [Cu(11-bromodipyrido[3,2-a:2',3'-c]phenazine)(PPh(3))(2)](BF(4)) at room temperature. The emission spectra suggest that the unusually long-lived excited states of the copper complexes result from metal-to-ligand charge transfer (MLCT) transitions as they are completely quenched in methanol. Electroluminescent films may be fabricated from these compounds; they show MLCT state emission even at low doping levels [<0.1% by weight in poly(vinylcarbazole) polymer matrix].     

Ruthenium(II) coordination chemistry of a fused donor-acceptor ligand: synthesis, characterization, and photoinduced electron-transfer reactions of [{Ru(bpy)2}(n)(TTF-ppb)](PF6)(2n) (n = 1, 2)

A pi-extended, redox-active bridging ligand 4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[2,3-a:3',2'-c]phenazine (L) was prepared via direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with 4,7-phenanthroline-5,6-dione. Reactions of L with [Ru(bpy)(2)Cl(2)] afforded its stable mono- and dinuclear ruthenium(II) complexes 1 and 2. They have been fully characterized, and their photophysical and electrochemical properties are reported together with those of [Ru(bpy)(2)(ppb)](2+) and [Ru(bpy)(2)(mu-ppb)Ru(bpy)(2)](4+) (ppb = dipyrido[2,3-a:3',2'-c]phenazine) for comparison. In all cases, the first excited state corresponds to an intramolecular TTF --> ppb charge-transfer state. Both ruthenium(II) complexes show two strong and well-separated metal-to-ligand charge-transfer (MLCT) absorption bands, whereas the (3)MLCT luminescence is strongly quenched via electron transfer from the TTF subunit. Clearly, the transient absorption spectra illustrate the role of the TTF fragment as an electron donor, which induces a triplet intraligand charge-transfer state ((3)ILCT) with lifetimes of approximately 200 and 50 ns for mono- and dinuclear ruthenium(II) complexes, respectively.     

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.     

Water-soluble, luminescent iridium(iii)-ytterbium(iii) complexes using dipyrido[3,2-a:2',3'-c]phenazine derivatives as bridging units

Amino-substituted dipyrido[3,2-a:2',3'-c]phenazine (L(1)) and dimethyl-dipyrido[3,2-a:2',3'-c]phenazine (L(2)) have been investigated as: (i) chromophores in cyclen-based ligands for lanthanide(iii) ions; (ii) ancillary co-ligands in cyclometalated iridium(iii) complexes; (iii) bridging, linker units in covalently linked, water-soluble bimetallic lanthanide(iii) iridium(iii) hybrid complexes. The dipyrido[3,2-a:2',3'-c]phenazine (dppz) derivatives can act as sensitising chromophores (λ(ex) 400 nm) for Yb(iii), resulting in characteristic near-IR emission at 950-1050 nm. The incorporation of dppz-type ligands into cyclometalated Ir(III) complexes of the general type [Ir(epqc)(2)(L(n))](PF(6)) (where epqc = ethylphenylquinoline carboxylate) gave luminescent species with solvent-sensitive emission properties. Steady state and time-resolved luminescence measurements on the water-soluble d-f hybrid species showed that Yb(III) can be sensitised using visible light.     

Dinuclear ruthenium(II) polypyridyl complexes containing large, redox-active, aromatic bridging ligands: synthesis, characterization, and intramolecular quenching of MLCT excited states

Two new ruthenium(II) polypyridyl dimers containing the large planar aromatic bridging ligands 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3' ',2'-l:2',3'-n]pentacene (tatpp) and 9,11,20,22-tetraazatetrapyrido[3,2-a:2'3'-c:3',2' '-l:2',3'-n]pentacene-10,21-quinone (tatpq) have been synthesized and characterized by (1)H and (13)C NMR, MALDI mass spectrometry, and elemental analyses. The electronic properties (UV-vis, redox, photophysical) of these dimers are analyzed in the context of orbital calculations (PM3 level) on the bridging ligands. A localized orbital model is proposed in which low-lying acceptor orbitals on the center portion of the ligands effectively quench the Ru(II)-based MLCT emission via a mechanism that can be viewed as intramolecular electron transfer to specific subunits of the bridges.     

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.     

Dinuclear monointercalating RuII complexes that display high affinity binding to duplex and quadruplex DNA

The DNA duplex binding properties of previously reported dinuclear Ru(II) complexes based on the ditopic ligands tetrapyrido[3,2-a:2',3'-c:3',2'-h:2',3'-j]phenazine (tppz) and tetraazatetrapyrido[3,2-a:2'3'-c:3',2'-l:2',3'-n]pentacene (tatpp) are reported. Photophysical and biophysical studies indicate that, even at high ionic strengths, these complexes bind to duplex DNA, through intercalation, with affinities that are higher than any other monointercalating complex and are only equalled by DNA-threaded bisintercalating complexes. Additional studies at high ionic strengths using the 22-mer d(AG(3)[T(2)AG(3)](3)) [G3] human telomeric sequence reveal that the dinuclear tppz-based systems also bind with high affinity to quadruplex DNA. Furthermore, for these complexes, quadruplex binding is accompanied by a distinctive blue-shifted "light-switch" effect, characterized by higher emission enhancements than those observed in the analogous duplex effect. Calorimetry studies reveal that the thermodynamics of duplex and quadruplex binding is distinctly different, with the former being entirely entropically driven and the latter being both enthalpically and entropically favored.     

Synthesis, characterization, and DNA binding properties of ruthenium(II) complexes containing the redox active ligand benzo[i]dipyrido[3,2-a:2',3'-c]phenazine-11,16-quinone

Synthetic methods toward ruthenium(II) complexes incorporating the benzo[i]dipyrido[3,2-a:2',3'-c]phenazine-11,16-quinone ligand, qdppn, are reported. In several cases, it was found that complexes containing coordinated benzo[i]dipyrido[3,2-a:2',3'-c]phenazine, dppn, could be chemically or photochemically oxidized to their qdppn analogues. Since this method was not possible in all the cases, a new, higher yielding, convenient synthesis of qdppn was developed. The crystal structure of the complex [Ru(phen)(2)(qppn)](PF(6))(2) (phen = 1,10-phenanthroline) which was synthesized from free qdppn reveals that a combination of π-π stacking between coordinated phen and qdppn units, as well as anion-ligand hydrogen bonding, define large hexagonal channels which are occupied by anions and solvent molecules. Electrochemical and photophysical studies reveal that the new qdppn-based complexes are not luminescent and, in contrast to their dppn analogues, they are also poor singlet oxygen sensitizers. Time-resolved studies and density functional theory (DFT) calculations indicate that optical properties of the new complexes are due to a short-lived charge separated state involving the quinone moiety of qdppn. The DNA binding properties of the new complexes have also been investigated. It was found that they are intercalators, displaying binding affinities which are comparable to their dppn analogues.     

Structure-activity relationship of photocytotoxic iron(III) complexes of modified dipyridophenazine ligands

Iron(III) complexes [FeL(B)] (1-5) of a tetradentate trianionic phenolate-based ligand (L) and modified dipyridophenazine bases (B), namely, dipyrido-6,7,8,9-tetrahydrophenazine (dpqC in 1), dipyrido[3,2-a:2',3'-c]phenazine-2-carboxylic acid (dppzc in 2), dipyrido[3,2-a:2',3'-c]phenazine-11-sulfonic acid (dppzs in 3), 7-aminodipyrido[3,2-a:2',3'-c]phenazine (dppza in 4) and benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn in 5), have been synthesized and their photocytotoxic properties studied along with their dipyridophenazine analogue (6). The complexes have a five electron paramagnetic iron(III) center, and the Fe(III)/Fe(II) redox couple appears at about -0.69 V versus SCE in DMF-0.1 M TBAP. The physicochemical data also suggest that the complexes possess similar structural features as that of its parent complex [FeL(dppz)] with FeO3N3 coordination in a distorted octahedral geometry. The DNA-complex and protein-complex interaction studies have revealed that the complexes interact favorably with the biomolecules, the degree of which depends on the nature of the substituents present on the dipyridophenazine ring. Photocleavage of pUC19 DNA by the complexes has been studied using visible light of 476, 530, and 647 nm wavelengths. Mechanistic investigations with inhibitors show formation of HO(?) radicals via a photoredox pathway. Photocytotoxicity study of the complexes in HeLa cells has shown that the dppn complex (5) is highly active in causing cell death in visible light with sub micromolar IC(50) value. The effect of substitutions and the planarity of the phenazine moiety on the cellular uptake are quantified by determining the total cellular iron content using the inductively coupled plasma-optical emission spectrometry (ICP-OES) technique. The cellular uptake increases marginally with an increase in the hydrophobicity of the dipyridophenazine ligands whereas complex 3 with dppzs shows very high uptake. Insights into the cell death mechanism by the dppn complex 5, obtained through DAPI nuclear staining in HeLa cells, reveal a rapid programmed cell death mechanism following photoactivation of complex 5 with visible light. The effect of substituent on the DNA photocleavage activity of the complexes has been rationalized from the theoretical studies.     

Non-covalent DNA binding and cytotoxicity of certain mixed-ligand ruthenium(II) complexes of 2,2'-dipyridylamine and diimines

A series of mixed ligand ruthenium(II) complexes [Ru(Hdpa)2(diimine)](ClO4)2, 1-5 where Hdpa is 2,2'-dipyridylamine and diimine is 1,10-phenanthroline (phen) and a modified/extended 1,10-phenanthroline such as, 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), 5-methyldipyrido[3,2-d:2',3'-f]quinoxaline (mdpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) have been isolated and characterized by analytical and spectral methods. The complex [Ru(Hdpa)2(phen)](PF6)2 1 has been structurally characterized and the coordination geometry around Ru(II) in it is described as distorted octahedral. 1H NMR spectral data reveal that 1-5 should have a C2 symmetry lying on the diimine plane due to the rapid flapping of the coordinated Hdpa ligands. The interaction of the complexes with calf thymus (CT) DNA has been explored by using absorption and emission spectral and viscometry and electrochemical techniques and the mode of DNA binding of the complexes has been proposed. The DNA binding affinity of the complexes decreases with decrease in number of planar aromatic rings in the co-ligand supporting the intercalation of the diimine co-ligands in between the DNA base pairs. Circular dichroic spectral studies reveal that the complexes 3-5 exhibit induced circular dichroism upon binding to CT DNA. Interestingly, upon interaction with CT DNA all the complexes show an increase in anodic current in the cyclic voltammograms suggesting that they are involved in electrocatalytic guanine oxidation. Interestingly, of all the complexes, only 5 alters the DNA superhelicity upon binding with supercoiled pBR322 DNA, which is consistent with its higher DNA binding affinity. Further, the cytotoxicities of the complexes against human cervical epidermoid carcinoma cell line (ME180) have been examined. Interestingly, 5 exhibits a cytotoxicity against ME180 higher than other complexes with potency approximately 8 times more than cisplatin for 24 h incubation but 4 times lower than cisplatin for 48 h incubation.     

Biocatalytic synthesis of the conjugated bridging ligand tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2'",3'"-j]phenazine (tpphz) and a dinuclear ruthenium complex

We have synthesized a fully conjugated aromatic bridging ligand, tetrapyrido[3,2-a:2',3'-c:3',2'-h:2' ",3'"-j]phenazine (tpphz), and a dinuclear ruthenium complex using Hematin as a biocatalyst.     

Fused donor-acceptor ligands in RuII chemistry: synthesis, electrochemistry and spectroscopy of [Ru(bpy)3-n(TTF-dppz)n](PF6)2.

Three ruthenium(II) polypyridine complexes of general formula [Ru(bpy)(3-n)(TTF-dppz)n](PF6)2 (n=1-3, bpy=2,2'-bipyridine), with one, two or three redox-active TTF-dppz (4',5'-bis(propylthio)tetrathiafulvenyl[i]dipyrido[3,2-a:2',3'-c]phenazine) ligands, were synthesised and fully characterised. Their electrochemical and photophysical properties are reported together with those of the reference compounds [Ru(bpy)3](PF6)2, [Ru(dppz)3](PF6)2 and [Ru(bpy)2(dppz)](PF6)2 and the free TTF-dppz ligand. All three complexes show intraligand charge-transfer (ILCT) fluorescence of the TTF-dppz ligand. Remarkably, the complex with n=1 exhibits luminescence from the Ru(2+)-->dppz metal-to-ligand charge-transfer ((3)MLCT) state, whereas for the other two complexes, a radiationless pathway via electron transfer from a second TTF-dppz ligand quenches the (3)MLCT luminescence. The TTF fragments as electron donors thus induce a ligand-to-ligand charge-separated (LLCS) state of the form TTF-dppz- -Ru(2+)-dppz-TTF(+). The lifetime of this LLCS state is approximately 2.3 micros, which is four orders of magnitude longer than that of 0.4 ns for the ILCT state, because recombination of charges on two different ligands is substantially slower.     

Trans ruthenium(II) complexes with NH-bridged tetradentate symmetric and asymmetric polypyridyl ligands

NH-Bridged tetradentate ligands were synthesized to achieve stable trans Ru(II) bis(polypyridyl) complexes. The polypyridyl part of the ligand was either symmetric, as in N,N-bis(1,10-phenanthroline-2-yl)amine (phen-NH-phen), or asymmetric, as in N-(1,10-phenanthroline-2-yl)-N-(6-yl-dipyridyl[2,3-a:2',3'-c]phenazine)amine (dppz-NH-phen). Protonation of phen-NH-phen with trifluoroacetic acid and the subsequent reaction with RuCl3 yield trans-[Ru(phen-NH-phen)Cl2]. The chloro ligands in this compound can easily be replaced by stronger ligands, such as CH3CN and DMSO. In this way, complexes trans-[Ru(phen-NH-phen)(CH3CN)(DMSO)](PF6)2 (1), trans-[Ru(phen-NH-phen)(DMSO)2](PF6)2 (2), and trans-[Ru(phen-NH-phen)(CH3CN)2](PF6)2 (3) were obtained. X-ray structures were determined for 1 and 3. Following a procedure similar to that used with phen-NH-phen, the complex trans-[Ru(dppz-NH-phen)(CH3CN)2](PF6)2 (4) was obtained. To our knowledge, this is the first reported trans ruthenium(II) bis(polypyridyl) complex with two different polypyridyl ligands in the equatorial plane.     

Dinuclear RuIIPHEHAT and -TPAC complexes: effects of the second RuII center on their spectroelectrochemical properties

Four novel dinuclear RuII compounds and, for comparison purposes, two corresponding mononuclear complexes containing the PHEHAT or TPAC ligand (PHEHAT=1,10-phenanthrolino[5,6-b]-1,4,5,8,9,12-hexaazatriphenylene and TPAC=tetrapyrido[3,2-a:2',3'-c:3' ',2' '-h:2' ',3' '-j]acridine) have been synthesized and characterized. Conclusions on the effects of dinucleation of these two bridging ligands can be drawn only for the compounds for which the results demonstrate that the bridging ligand is involved in the first electrochemical reduction and lowest emission energy. The behavior of these complexes, which is not always predictable, is discussed, and the differences are highlighted in this work. Interestingly, all of the compounds are luminescent except one dinuclear species, [(phen)2Ru-mu-PHEHAT-Ru(TAP)2]4+, which does not luminesce in MeCN and BuCN at room temperature.     

Derivatives of dipyrido[3,2-a:2',3'-c]phenazine and its ruthenium complexes, influence of arylic substitution on photophysical properties

The synthesis and photophysical properties of a series of substituted dipyridophenazine (dppz) ruthenium complexes of the type [(tbbpy)2Ru(dppz-R2)]2+ (where tbbpy = 4,4-tert-butyl-2,2-bipyridine and dppz = dipyrido[3,2-a:2',3'-c]phenazine and R represents substitution at the 11 and 12 position with: Br, phenyl, 4-tert-butyl-phenyl and para-biphenyl) are described. The ligands could be obtained in high yields using Suzuki-type coupling reactions, an approach which also has been successfully applied to the analogous dppz-Br2 ruthenium complex. All compounds are fully characterised by NMR, MS and UV-vis spectroscopy. The solid state structures of dppz-bi-para-biphenyl and the ruthenium complex [(tbbpy)2Ru(dppz-Br2)]2+ are also reported. The investigation of the free ligands reveals a pronounced effect of the arylic substitution on absorption and emission properties. These properties are mirrored in the corresponding complexes, which possess emission lifetimes of up to 900 ns. The resonance Raman investigation of the complex [(tbbpy)2Ru(dppz-Br2)]2+ supports the assumption that the excited state properties of the substituted complexes are related to the parent [(bpy)2Ru(dppz)]2+ compound, but that important differences may be expected based on the differences observed in the lowest energy absorption band.     

新型双核配合物的形成及荧光性质研究

利用光谱学方法研究了[Ru(bpy)2TPPHZ]2+(TPPHZ=四吡啶[3,2-a: 2',3'-c: 3",2"-h: 2'",3'"-j]吩嗪)和[Ru(bpy)2ODHIP]2+(ODHIP=3,4-二羟基-咪唑并[4,5-f][1,10]邻菲咯啉)与Ni2+的配位情况及配位后的荧光性质变化, 探讨了配合物与Ni2+配位形成双核配合物后与DNA的作用机制变化. 结果表明, [Ru(bpy)2TPPHZ]2+和[Ru(bpy)2ODHIP]2+均可与Ni2+配位, 形成双核配合物[Ru(bpy)2(TPPHZ)Ni]4+和[Ru(bpy)2(ODHIP)Ni]4+, 配合物的荧光强度随着Ni2+浓度的增加而减弱. 与DNA作用后, 配合物仍可与Ni2+配位形成双核配合物, [Ru(bpy)2(TPPHZ)Ni]4+的荧光几乎完全消失, 同时配合物与DNA保持插入模式作用, 而配合物[Ru(bpy)2(ODHIP)Ni]4+与DNA的作用则由沟面结合改为插入结合, 同时配合物的荧光减弱.     

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.     

△,Λ-[Co(phen)2tpphz]^3+与B - DNA相互作用的分子 模拟

针对国际上对金属配合物同DNA间作用机量的争议,采用分子模拟手段在MM2力场下,搭建并优化了手性金属配合物△,Λ-[Co(phen)2tpphz]^3+与B-DNA[d(GTCGATCGAC)2]的模型,继而对其相互作用进行了模拟,得出的结论是：对所采用的B-DNA片断,该金属配合物有明显的立体选择性△型配合物从小沟插入占明显优势,而且,总体来看,从AT区插入更易进行。     

Electrochemical and photophysical properties of DNA metallo-intercalators containing the ruthenium(II) tris(1-pyrazolyl)methane unit

Three new ruthenium(II) complexes containing the tris(1-pyrazolyl)methane (tpm) ligand have been prepared: [Ru(tpm)(L)(dppn)]n+ (where n = 1; L = Cl (5), n = 2; L = MeCN (6) and pyridine (7); dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine). Complex 6 was structurally characterized by single-crystal X-ray diffraction. Binding parameters of these complexes with calf thymus DNA are reported and compared to those obtained for a previously reported monocation, [RuCl(tpm)(dppz)]+. Binding studies with the dications and the synthetic oligonucleotides poly(dA).poly(dT) and poly(dG).poly(dC) have also been determined. Photophysical and electrochemical properties of 5-7 have been investigated and compared with their dipyridophenazine (dppz) analogues.