Synthesis, structure, characterization, and photophysical studies of a new platinum terpyridyl-based triad with covalently linked donor and acceptor groups

A new terpyridyl-containing Pt triad [Pt(pytpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)](PF6)2 (4), where pytpy = 4'-(4-pyridin-1-ylmethylphenyl)-[2,2';6',2' ']terpyridine and p-CC-C6H4-NH-CO-C6H2(OMe)3 = N-(4-ethynylphenyl)-3,4,5-trimethoxybenzamide, has been synthesized and structurally characterized. The related donor-chromophore dyad [Pt(ttpy)(p-CC-C6H4-NH-CO-C6H2(OMe)3)]PF6 2, where ttpy = 4'-p-tolyl-[2,2';6',2' ']terpyridine, and the chromophore-acceptor dyad [Pt(pytpy)(CCC6H5)](PF6)2 (3), where CCC6H5 = ethynylbenzene, have also been studied. The multistep syntheses culminate with a CuI-catalyzed coupling reaction of the respective acetylene with either [Pt(ttpy)Cl]PF6 or [Pt(pytpy)Cl](PF6)2. X-ray and spectroscopic studies support assignment of a distorted square planar environment around the Pt(II) ion with three of its coordination sites occupied by the terpyridyl N-donors and the fourth coordination site occupied by the acetylenic carbon. Although the parent compound [Pt(ttpy)(CCC6H5)]PF6 (1) is brightly luminescent in fluid solution at 298 K, dyad 2 as well as triad 4 exhibit complete quenching of the emission. The chromophore-acceptor (C-A) dyad 3 displays weak solution luminescence at room temperature with a phi(rel)(em) of 0.011 (using Ru(bpy)3(2+) as a standard with phi(rel)(em) = 0.062). Electrochemically, the donor-chromophore (D-C) dyad and the donor-chromophore-acceptor (D-C-A) triad exhibit both metal-based and donor ligand-based oxidations, whereas the triad and the C-A dyad show the expected pyridinium- and terpyridine-based reductions. Transient absorption studies of the dyad and triad systems indicate that although the trimethoxybenzene group acts as a reductive donor, in the present system, the pyridinium group fails to act as an acceptor.     

A platinum-ruthenium dinuclear complex bridged by bis(terpyridyl)xanthene

4,5-Bis(terpyridyl)-2,7-di-tert-butyl-9,9-dimethylxanthene (btpyxa) was prepared to serve as a new bridging ligand via Suzuki coupling of terpyridin-4'-yl triflate and 2,7-di-tert-butyl-9,9-dimethylxanthene-4,5-diboronic acid. The reaction of btpyxa with either 1 equiv or an excess of PtCl(2)(cod) (cod = 1,5-cyclooctadiene) followed by anion exchange afforded mono- and dinuclear platinum complexes [(PtCl)(btpyxa)](PF(6)) ([1](PF(6))) and [(PtCl)(2)(btpyxa)](PF(6))(2) ([2](PF(6))(2)), respectively. The X-ray crystallography of [1](PF(6)).CHCl(3) revealed that the two terpyridine units in the ligand are nearly parallel to each other. The heterodinuclear complex [(PtCl)[Ru((t)Bu(2)SQ)(dmso)](btpyxa)](PF(6))(2) ([4](PF(6))(2)) (dmso = dimethyl sulfoxide; (t)Bu(2)SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) and the monoruthenium complex [Ru((t)Bu(2)SQ)(dmso)(trpy)](PF(6)) ([5](PF(6))) (trpy = 2,2':6',2' '-terpyridine) were also synthesized. The CV of [2](2+) suggests possible electronic interaction between the two Pt(trpy) groups, whereas such an electronic interaction was not suggested by the CV of [4](2+) between Pt(trpy) and Ru((t)Bu(2)SQ) frameworks.     

A novel heteroditopic terpyridine-pincer ligand as building block for mono- and heterometallic Pd(II) and Ru(II) complexes

A palladium-catalyzed Stille coupling reaction was employed as a versatile method for the synthesis of a novel terpyridine-pincer (3, TPBr) bridging ligand, 4'-{4-BrC6H2(CH2NMe2)2-3,5}-2,2':6',2' '-terpyridine. Mononuclear species [PdX(TP)] (X = Br, Cl), [Ru(TPBr)(tpy)](PF6)2, and [Ru(TPBr)2](PF6)2, synthesized by selective metalation of the NCNBr-pincer moiety or complexation of the terpyridine of the bifunctional ligand TPBr, were used as building blocks for the preparation of heterodi- and trimetallic complexes [Ru(TPPdCl)(tpy)](PF6)2 (7) and [Ru(TPPdCl)2](PF6)2 (8). The molecular structures in the solid state of [PdBr(TP)] (4a) and [Ru(TPBr)2](PF6)2 (6) have been determined by single-crystal X-ray analysis. Electrochemical behavior and photophysical properties of the mono- and heterometallic complexes are described. All the above di- and trimetallic Ru complexes exhibit absorption bands attributable to (1)MLCT (Ru --> tpy) transitions. For the heteroleptic complexes, the transitions involving the unsubstituted tpy ligand are at a lower energy than the tpy moiety of the TPBr ligand. The absorption bands observed in the electronic spectra for TPBr and [PdCl(TP)] have been assigned with the aid of TD-DFT calculations. All complexes display weak emission both at room temperature and in a butyronitrile glass at 77 K. The considerable red shift of the emission maxima relative to the signal of the reference compound [Ru(tpy)2]2+ indicates stabilization of the luminescent 3MLCT state. For the mono- and heterometallic complexes, electrochemical and spectroscopic studies (electronic absorption and emission spectra and luminescence lifetimes recorded at room temperature and 77 K in nitrile solvents), together with the information gained from IR spectroelectrochemical studies of the dimetallic complex [Ru(TPPdSCN)(tpy)](PF6)2, are indicative of charge redistribution through the bridging ligand TPBr. The results are in line with a weak coupling between the {Ru(tpy)2} chromophoric unit and the (non)metalated NCN-pincer moiety.     

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.     

Water-soluble alkylated bis{4'-(4-pyridyl)-2,2':6',2'-terpyridine}ruthenium(II) complexes for use as photosensitizers in water oxidation: a complementary experimental and TD-DFT investigation

A series of N-alkylated derivatives [RuL(2)][PF(6)](4) has been prepared from [Ru(pytpy)(2)][PF(6)](2) (N-alkyl substituent = 4-cyanobenzyl, 4-nitrobenzyl, ethyl, cyanomethyl, allyl, octyl). Solution NMR spectroscopic, electrochemical and photophysical properties are reported, along with the single crystal structure of [Ru(4)(2)][PF(6)](4)·H(2)O (4 = 4'-(4-(1-ethylpyridinio))-2,2':6',2'-terpyridine). Anion exchange leads to the water-soluble [RuL(2)][HSO(4)](4) salts (N-alkyl substituent = benzyl, 4-cyanobenzyl, 4-nitrobenzyl, ethyl, cyanomethyl, allyl, octyl) and the NMR spectroscopic signatures of pairs of hexafluoridophosphate and hydrogensulfate salts are compared. The change in anion has little effect on the energies of absorptions in the electronic spectra, although for all complexes, decreases in extinction coefficients are observed. The emission spectra and lifetimes for the hexafluoridophosphate and hydrogensulfate salts show similar trends; all exhibit an emission close to 720-730 nm (λ(ex) = 510 nm). For a given ligand, L, the emission lifetime decreases on going from [RuL(2)][PF(6)](4) to [RuL(2)][HSO(4)](4). However, trends are the same for both salts, i.e. the longest lived emitters are observed for N-ethyl, N-octyl and N-benzyl derivatives, and the shortest lived emitters are those containing cyano or nitro groups. Significantly, in the absorption spectra of the complexes, there is little variation in the energy of the MLCT band, suggesting that the character of the ligand orbital involved in the transition contains no character from the N-substituent. We have addressed this by carrying out a complementary DFT and TD-DFT study. Calculated absorption spectra predict a red shift in λ(max) on going from [Ru(pytpy)(2)](2+) to [RuL(2)](4+), and little variation in λ(max) within the series of [RuL(2)](4+) complexes; these results agree with experimental observations. Analysis of the compositions of the MOs involved in the MLCT transitions explain the experimental observations, showing that there is no contribution from orbitals on the N-alkyl substituents, consistent with the fact that the nature of the N-substituents has little influence on the energy of the MLCT band. The theoretical results also reveal satisfactory agreement between calculated and crystallographic data for [Ru(1)(2)](4+) (1 = 4'-(4-(1-benzylpyridinio))-2,2':6',2'-terpyridine) and [Ru(4)(2)](4+).     

2,2':6',2'-terpyridine substituted in the 4'-position by the solubilizing and sterically demanding tert-butyl group: a surprisingly new ligand

We describe the synthesis and characterization of 4'-tert-butyl-2,2':6',2'-terpyridine (4'-(t)Butpy, 1), a convergent tpy ligand that exhibits both a sterically demanding and solubilizing 4'-substituent. In the solid state, molecules of 1 pack with alternating tpy and tert-butyl domains, and the bulky alkyl substituents prevent the molecules from engaging in the face-to-face π-interactions which are typical of simple tpy ligands. Instead, the predominant packing forces involve CH···N hydrogen bonds and weak CH···π contacts. The syntheses of the homoleptic complexes [M(1)(2)][PF(6)](2) (M = Fe, Co, Zn and Ru) and the heteroleptic [Ru(tpy)(1)][PF(6)](2) are described. The complexes have been fully characterized in solution, including the (1)H NMR spectroscopic characterization of the paramagnetic [Co(1)(2)][PF(6)](2). Cyclic voltammetric data are consistent with the tert-butyl substituent being slightly electron releasing. The single crystal structures of [Zn(1)(2)][PF(6)](2) and [Ru(1)(2)][PF(6)](2) have been determined; the compounds are essentially isomorphous. The packing of the cations is such that the tert-butyl substituents are accommodated in pockets between the tpy domains of adjacent cations, and as a consequence, the {M(tpy)(2)}-embrace that is a ubiquitous feature of many related structures is not observed.     

Rapid energy transfer in bichromophoric tris-bipyridyl/cyclometallated ruthenium(II) complexes

The synthesis, characterization, and photophysical properties of the N6-N5C bichromophoric [(bpy)2Ru(I)Ru(ttpy)][PF6]3 (bpy is 2,2'-bipyridine and ttpy is 4'-p-tolyl-2,2':6',2'-terpyridine) and [(bpy)2Ru(II)Ru(ttpy)][PF6]3 (I and II are bpy-dipyridylbenzene ditopic ligands bridged by an ethynyl and phenyl unit, respectively) complexes are reported together with the model mononuclear complexes [(bpy)2Ru(I)][PF6]2, [(bpy)2Ru(II)][PF6]2, [Ru(VI)(ttpy)][PF6] (VI is 3,5-di(2-pyridyl)-biphenyl) and [Ru(dpb)(ttpy)][PF(6)] (Hdpb is 1,3-di(2-pyridyl)-benzene). The electrochemical data show that there is little ground state electronic communication between the metal centers in the bimetallic complexes. Selective excitation of the N(5)C unit in the bichromophoric systems leads to luminescence typical for a bis-tridentate cyclometallated ruthenium complex and is similar to the [Ru(VI)(ttpy)][PF6] model complex. In contrast, the luminescence from the tris-bidentate N6 unit is efficiently quenched by energy transfer to the N5C unit. The energy transfer rate has been determined by femtosecond pump-probe measurements to 0.7 ps in the ethynyl-linked [(bpy)2Ru(I)Ru(ttpy)][PF6]3 and to 1.5 ps in the phenyl-linked [(bpy)2Ru(II)Ru(ttpy)][PF6]3 (in acetonitrile solution at 298 K), and is inferred to occur via a Dexter mechanism.     

Monometallic and dimetallic ruthenium(II)-terpyridine complexes employing the tetradentate ligands dipyridylpyrazolyl,dipyridyloxadiazole, and their dimethyl derivatives

The tetradentate ligands, 2,2'-(1H-pyrazole-3,5-diyl)bis(4- methylpyridine) (4,4'-Me2dppzH), 2,2'-(1H-pyrazole-3,5-diyl)bis(6-methylpyridine) (6,6'-Me2dppzH), 3,5-di(pyrid-2-yl)pyrazole (dppzH), and dipyridyloxadiazole (dpo) react with either Ru(trpy)Cl3 or trans-Ru(trpy)Cl2(NCCH3), where trpy is 2,2',2'-terpyridine, to form a variety of Ru(II) complexes. Among these are the symmetrical chloro-bridged Ru(II) dimer and the "in" and "out" geometric isomers of the monometallic Ru(II) containing species where "in" and "out" refer to the orientation of the Ru-Cl vector relative to the centroid of the ligand backbone. Thirteen complexes were prepared and painstakingly purified by careful recrystallization and/or exhaustive column chromatography. These complexes were characterized by 1H and 13C NMR, electronic absorption, and infrared spectroscopy. Additionally, [Ru2(tryp)2(6,6'-Me2dppz)mu-Cl](BF4)2 (3b(BF4)2), [Ru2(trpy)2(4,4'-Me2dppz)mu-Cl](PF6)2.0.5MeOH (3c), [Ru2(trpy)2(6,6'-Me2dppz)(CH2C(O)CH3)](PF6)2.0.5(CH3)2CO (9b), "in"-[Ru(trpy)(4,4'-Me2dppz)Cl](PF6).(CH3)2CO (1c), and "out"-[Ru(trpy)(dpo)Cl](PF6).(CH3)2CO (2d) were characterized by X-ray crystallography. Several ligand substitution reactions were attempted. For example, [Ru2(trpy)2(6,6'-Me2dppz)mu-Cl](BF4)2 (3b) was reacted with hydroxide ion to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-OH](PF6)2 (6b). Complex 6b reacts with benzyl bromide to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-Br](PF6)2 (7b) or with (CH3)3Sil to produce [Ru2(trpy)2(6,6'-Me2dppz)mu-I](PF6)2 (8b). of 6b with acetone forms the methyl enolate complex [Ru2(trpy)2(6,6'-Me2dppz)(CH2COCH3)](PF6)2 (9b) while, analogously to a Cannizarro reaction, the reaction with benzaldehyde forms the bridging benzoate complex [Ru2(trpy)2(6,6'-Me2dppz)(C6H4CO2)](PF6)2 (11b). The bridging azide complex [Ru2(trpy)2(6,6'-Me2dppz)mu-N3](PF6)2 (10b) is formed by reaction of 6b with (CH3)3-SiN3. Additionally, the chloride ligands of the monometallic complexes of "in"-[Ru(trpy)(dpo)Cl](PF6) (1d), "in"-[Ru(trpy)(4,4'-Me2dpo)Cl](PF6)] (1e), and "out"-[Ru(trpy)(dpo)Cl](PF6) (2d) were substituted with water to form their respective aqua complexes, 4d, 4e, and 5d. All of the complexes exhibit broad unsymmetrial absorption bands in the visible portion of the electromagnetic spectrum. The dimetallic complexes 3b and 3c exhibit two, 1e- reversible oxidation waves at +0.72 and +1.15 V, and at +0.64 and +1.13 V, respectively. These complexes were not emissive.     

Synthesis, luminescence, and electrochemical studies of tris(homoleptic) ruthenium(II) and osmium(II) complexes of 6'-tolyl-2,2':4',2'-terpyridine

The synthesis and photophysical and electrochemical properties of tris(homoleptic) complexes [Ru(tpbpy)3](PF6)2 (1) and [Os(tpbpy)3](PF6)2 (2) (tpbpy = 6'-tolyl-2,2':4',2' '-terpyridine) are reported. The ligand tpbpy is formed as the side product during the synthesis of 4'-tolyl-2,2':6',2' '-terpyridine (ttpy) and characterized by single-crystal X-ray diffraction: monoclinic, P21/c. The tridentate tpbpy coordinates as a bidentate ligand. The complexes 1 and 2 exhibit two intense absorption bands in the UV region (200-350 nm) assignable to the ligand-centered (1LC) pi-pi* transitions. The ruthenium(II) complex exhibits a broad absorption band at 470 nm while the osmium(II) complex exhibits an intense absorption band at 485 nm and a weak band at 659 nm assignable to the MLCT (dpi-pi*) transitions. A red shifting of the dpi-pi* MLCT transition is observed on going from the Ru(II) to the Os(II) complex as expected from the high-lying dpi Os orbitals. These complexes exhibit ligand-sensitized emission at 732 and 736 nm, respectively, upon light excitation onto their MLCT band through excitation of higher energy LC bands at room temperature. The MLCT transitions and the emission maxima of 1 and 2 are substantially red-shifted compared to that of [Ru(bpy)3](PF6)2 and [Os(bpy)3](PF6)2. The emission of both the complexes in the presence of acid is completely quenched indicating that the emission is not due to the protonation of the coordinated ligands. Our results indicate the occurrence of intramolecular energy transfer from the ligand to the metal center. Both the complexes undergo quasi-reversible metal-centered oxidation, and the E1/2 values for the M(II)/M(III) redox couples (0.94 and 0.50 V versus Ag/Ag+ for 1 and 2, respectively) are cathodically shifted with respect to that of [Ru(bpy)3](PF6)2 and [Os(bpy)3](PF6)2 (E1/2 = 1.28 and 1.09 V versus Ag/Ag+, respectively). The tris(homoleptic) Ru(II) and Os(II) complexes 1 and 2 could be used to construct polynuclear complexes by using the modular synthetic approach in coordination compounds by exploiting the coordinating ability of the pyridine substituent. Furthermore, these complexes offer the possibility of studying the influence of electron-withdrawing and electron-donating substituents on the photophysical properties of Ru(II) and Os(II) polypyridine complexes.     

1,10]-Phenanthrolin-2-yl ketones and their coordination chemistry

A synthetic protocol involving the Friedl?nder reaction of 8-amino-7-quinolinecarbaldehyde followed by potassium dichromate oxidation was applied to 2,3,4-pentanetrione-3-oxime and 1-(pyrid-2'-yl)propane-1,2-dione-1-oxime to provide the ligands di-(phenathrolin-2-yl)-methanone (1) and phenanthrolin-2-yl-pyrid-2-yl-methanone (8), respectively. Ligand 1 complexed as a planar tetradentate with Pd(II) to form [Pd(1)](BF4)2 and with Ru(II) and two 4-substituted pyridines (4-R-py) to form [Ru(1)(4-R-py)2](PF6)2 where R = CF3, CH3, and Me2N. With [Ru(bpy)2Cl2], the dinuclear complex [(bpy)2Ru(1)Ru(bpy)2](PF6)4 was formed (bpy = 2,2'-bipyridine). Ligand 8 afforded the homoleptic Ru(II) complex [Ru(8)2](PF6)2, as well as the heteroleptic complex [Ru(8)(tpy)](PF6)2 (tpy = 2,2';6,2'-terpyridine). The ligands and complexes were characterized by their NMR and IR spectra, as well as an X-ray structure determination of [Ru(1)(4-CH3-py)2](PF6)2. Electrochemical analysis indicated metal-based oxidation and ligand-based reduction that was consistent with results from electronic absorption spectra. The complexes [Ru(1)(4-R-py)2](PF6)2 were sensitive to the 4-substituent on the axial pyridine: electron donor groups facilitated the oxidation while electron-withdrawing groups impeded it.     

cis-[Ru(2,2':6',2' '-terpyridine)(DMSO)Cl(2)]: useful precursor for the synthesis of heteroleptic terpyridine complexes under mild conditions

[Ru(II)(terpy)(DMSO)Cl(2)] complexes were synthesized as a 5/1 mixture of cis and trans isomers, and their reactivities with CO and with substituted 2,2':6',2' '-terpyridine (terpy) moieties have been investigated. The structure of a trans isomer and its CO adduct have been unambiguously assigned by spectroscopy and X-ray diffraction. The [Ru(terpy)(terpy-Br)](2+) complex prepared either from the cis-[Ru(II)(terpy)(DMSO)Cl(2)] or from the cis-[Ru(II)(terpy-Br)(DMSO)Cl(2)] precursor appeared to be reactive in cross-coupling reactions promoted by low-valent palladium(0) and is an attractive target for the stepwise synthesis of polynuclear complexes bearing vacant coordination sites (terpy-Br for 4'-bromo-2,2':6',2' '-terpyridine). Several bipyridine, phenanthroline, and bipyrimidine complexes were prepared this way and their optical and redox properties determined and discussed.     

Effect of adenine moiety on DNA binding property of copper(II)-terpyridine complexes

Two novel copper(ii) terpyridine complexes, [Cu(atpy)(NO(3))(H(2)O)](NO(3)).3H(2)O () and [Cu(ttpy)(NO(3))(2)] () (atpy = 4'-p-N9-adeninylmethylphenyl-2,2':6,2'-terpyridine; ttpy = 4'-p-tolyl-2,2':6,2'-terpyridine) have been prepared and structurally characterized by X-ray crystallography. Both complexes show a CuN(3)O(2) coordination in a square pyramidal (4 + 1) geometry with terpyridine acting as an equatorial ligand. For complex , intermolecular AA base pairing interaction is observed between N(6) and N(1) of adjacent adenines with N(6)N(1) of 3.027(7) A. A molecular dynamics simulation of the DNA binding of two complexes showed that the adenine moiety plays an important role in the intercalation of into DNA. This is verified by UV, fluorescence, circular dichroism and flow linear dichroism studies. The promotional effect from the adenine moiety to the intracellular DNA binding of complex is also confirmed by the inductively coupled plasma mass (ICP-MS) spectrometry data which showed a significant higher copper content in DNA isolated from complex treated MCF-7 and HeLa cells.     

Reversible molecular switching of ruthenium bis(bipyridyl) groups bonded to oligothiophenes: effect on electrochemical and spectroscopic properties

We report the preparation of complexes in which ruthenium(II) bis(bipyridyl) groups are coordinated to oligothiophenes via a diphenylphosphine linker and a thienyl sulfur (P,S bonding) to give [Ru(bpy)(2)PT(3)-P,S](PF(6))(2) (bpy = 2,2'-bipyridyl, PT(3) = 3'-(diphenylphosphino)-2,2':5',2' '-terthiophene), [Ru(bpy)(2)PMeT(3)-P,S](PF(6))(2) (PMeT(3) = 3'-(diphenylphosphino)-5-methyl-2,2':5',2' '-terthiophene), [Ru(bpy)(2)PMe(2)T(3)-P,S](PF(6))(2) (PMe(2)T(3) = 5,5' '-dimethyl-3'-(diphenylphosphino)-2,2':5',2' '-terthiophene), and [Ru(bpy)(2)PDo(2)T(5)-P,S](PF(6))(2) (PDo(2)T(5) = 3,3' ' '-didodecyl-3' '-diphenylphosphino-2,2':5',2' ':5' ',2' ':5' ',2' ' '-pentathiophene). These complexes react with base, resulting in the complexes [Ru(bpy)(2)PT(3)-P,C]PF(6), [Ru(bpy)(2)PMeT(3)-P,C]PF(6), [Ru(bpy)(2)PMe(2)T(3)-P,C]PF(6), and [Ru(bpy)(2)PDo(2)T(5)-P,C]PF(6), where the thienyl carbon is bonded to ruthenium (P,C bonding). The P,C complexes revert back to the P,S bonding mode by reaction with acid; therefore, metal-thienyl bonding is reversibly switchable. The effect of interaction of the metal groups in the different bonding modes with the thienyl backbone is reflected by changes in alignment of the thienyl rings in the solid-state structures of the complexes, the redox potentials, and the pi --> pi transitions in solution. Methyl substituents attached to the terthiophene groups allow observation of the effect of these substituents on the conformational and electronic properties and aid in assignments of the electrochemical data. The PT(n)() ligands bound in P,S and P,C bonding modes also alter the electrochemical and spectroscopic properties of the ruthenium bis(bipyridyl) group. Both bonding modes result in quenching of the oligothiophene luminescence. Weak, short-lived Ru --> bipyridyl MLCT-based luminescence is observed for [Ru(bpy)(2)PDo(2)T(5)-P,S](PF(6))(2), [Ru(bpy)(2)PT(3)-P,C]PF(6), [Ru(bpy)(2)PMeT(3)-P,C]PF(6), and [Ru(bpy)(2)PMe(2)T(3)-P,C]PF(6), and no emission is observed for the alternate bonding mode of each complex.     

TiO2纳米颗粒对钌(II)三联吡啶配合物光损伤小牛胸腺DNA能力的影响

由于极短的激发态寿命, 钌(II)三联吡啶配合物对脱氧核糖核酸(DNA)的光损伤能力低下. 设计合成了三个钌(II)三联吡啶配合物[Ru(ttp)(tpy)]^2＋ (1), [Ru(ttp-COOH)(tpy)]^2＋ (2)和[Ru(ttp-COOH)(tpy-pyr)]^2＋ (3), 其中tpy为2,2':6',2"-三联吡啶, ttp为4′-(4-甲苯基)-2,2':6',2"-三联吡啶, ttp-COOH为4′-(4-羧基苯基)-2,2':6',2"-三联吡啶, tpy-pyr为4'-(1-芘基)-2,2':6',2"-三联吡啶. 比较了TiO₂纳米颗粒对它们光损伤小牛胸腺DNA的影响. 发现TiO₂纳米颗粒在空气和氩气条件下均可显著提高配合物3光损伤DNA的能力. TiO₂纳米颗粒和配合物3间的光诱导电子转移作用及其该作用生成的钌(III)物种可能是促进配合物3对DNA光损伤的主要原因.     

Substituents dependent capability of bis(ruthenium-dioxolene-terpyridine) complexes toward water oxidation

The bridging ligand, 1,8-bis(2,2':6',2'-terpyrid-4'-yl)anthracene (btpyan) was synthesized by the Miyaura-Suzuki cross coupling reaction of anthracenyl-1,8-diboronic acid and 4'-triflyl-2,2':6'-2'-terpyridine in the presence of Pd(PPh(3))(4) (5 mol%) with 68% in yield. Three ruthenium-dioxolene dimers, [Ru(2)(OH)(2)(dioxolene)(2)(btpyan)](0) (dioxolene = 3,6-di-tert-butyl-1,2-benzosemiquinone ([1](0)), 3,5-dichloro-1,2-benzosemiquinone ([2](0)) and 4-nitro-1,2-benzosemiquinone ([3](0))) were prepared by the reaction of [Ru(2)Cl(6)(btpyan)](0) with the corresponding catechol. The electronic structure of [1](0) is approximated by [Ru(II)(2)(OH)(2)(sq)(2)(btpyan)](0) (sq = semiquinonato). On the other hand, the electronic states of [2](0) and [3](0) are close to [Ru(III)(2)(OH)(2) (cat)(2)(btpyan)](0) (cat = catecholato), indicating that a dioxolene having electron-withdrawing groups stabilizes [Ru(III)(2)(OH)(2)(cat)(2)(btpyan)](0) rather than [Ru(II)(2)(OH)(2)(sq)(2)(btpyan)](0) as resonance isomers. No sign was found of deprotonation of the hydroxo groups of [1](0), whereas [2](0) and [3](0) showed an acid-base equilibrium in treatments with t-BuOLi followed by HClO(4). Furthermore, controlled potential electrolysis of [1](0) deposited on an ITO (indium-tin oxide) electrode catalyzed the four-electron oxidation of H(2)O to evolve O(2) at potentials more positive than +1.6 V (vs. SCE) at pH 4.0. On the other hand, the electrolysis of [2](0) and [3](0) deposited on ITO electrodes did not show catalytic activity for water oxidation under similar conditions. Such a difference in the reactivity among [1](0), [2](0) and [3](0) is ascribed to the shift of the resonance equilibrium between [Ru(II)(2)(OH)(2)(sq)(2)(btpyan)](0) and [Ru(III)(2)(OH)(2)(cat)(2)(btpyan)](0).     

Acid-base equilibria of various oxidation states of aqua-ruthenium complexes with 1,10-phenanthroline-5,6-dione in aqueous media

Syntheses and pH dependent electrochemical properties of aqua-ruthenium(II) complexes, [Ru(trpy)(PDA-N,N')(OH2)](ClO4)2 ([1](ClO4)2) and [Ru(trpy)(PD-N,N')(OH2)](ClO4)2 ([2](ClO4)2) (trpy = 2,2':6',2'-terpyridine, PDA = 6-acetonyl-6-hydroxy-1,10-phenanthroline-5-one, PD = 1,10-phenanthroline-5,6-dione) are presented. Treatment of [Ru(trpy)(PD-N,N')Cl](PF6) with AgClO4 in a mixed solvent of acetone and H2O selectively produced the acetonyl-PD complex [1](ClO4)2, and the similar treatment in a mixed solvent of 2-methoxyethanol and H2O gave the PD complex [2](ClO4)2. The molecular structures of both complexes were determined by X-ray structural analysis. The proton dissociation constants of various oxidations state of [1]2+ and [2]2+ were evaluated by simulation of E(1/2) values of those redox potentials depending on pH. The simulation revealed that the acetonyl-PD complex [1]2+ underwent successive Ru(II)/Ru(III) and Ru(III)/Ru(IV) redox couples though the two redox reactions were not separated in the cyclic voltammograms. The redox behavior of [2]2+ in H2O is reasonably explained by not only the similar successive metal-centered redox reactions but also simultaneous two-electron quinone/catechol redox couple of the PD ligand including the contribution of hydration on a carbonyl carbon.     

Synthesis and properties of the elusive ruthenium(II) complexes of 4'-cyano-2,2':6',2' '-terpyridine

The heteroleptic and homoleptic ruthenium(II) complexes of 4'-cyano-2,2':6',2' '-terpyridine are synthesized by palladium catalyzed cyanation of the corresponding Ru(II) complexes of 4'-chloro-2,2':6',2' '-terpyridine. The introduction of the strongly electron-withdrawing cyano group into the Ru(tpy)(2)(2+) moiety dramatically changes its photophysical and redox properties as well as prolongs its room temperature excited-state lifetime.     

Self-assembled monolayers of Ru/Os dinuclear complexes: probing monolayer structure and interaction energies by electrochemical means

Monolayers of [Ru(bpy)2(micro-1)M2][PF6]4 salts (M = Os, Ru; bpy = 2,2'-bipyridine, 1 = 4'-(2,2'-bipyridin-4-yl)-2,2':6',2' '-terpyridine, tpy = 2,2':6',2' '-terpyridine, and 2 = 4'-(4-pyridyl)-2,2':6',2' '-terpyridine) were self-assembled on platinum and investigated by fast-scan electrochemistry. The electrochemistry of the complexes in solution and confined to the surface in self-assembled monolayers (SAMs) exhibited an almost ideal behavior. Scan-rate-dependent measurements of the peak current density (jp) were used to determine interaction energies within the monolayer. It is shown that the tpy coordination sites of the dinuclear complexes interact more strongly within the SAM than the bipyridine-coordinated fragments. This result was supported by peak potential shifts, which are due to interaction forces in SAMs. The alignment of the rodlike complexes relative to the surface is discussed, and the results of molecular mechanics calculations indicate that the species adopt a tilted orientation.     

Two-photon luminescence from polar bis-terpyridyl-stilbene derivatives of Ir(III) and Ru(II)

Four structurally related iridium(III) and ruthenium(II) complexes bearing two polar terpyridyl-stilbene derived chromophores 4-(4-{2-[4-(methoxy)phenyl]ethenyl}phenyl)-2,2'-6',2'-terpyridine (ttpyeneanisole) and 4-(4-{2-[phenyl]ethenyl}phenyl)-2,2'-6',2'-terpyridine (tpystilbene) have been synthesised and characterised in the solid state and in solution. In the solid state, the dihedral angle subtending the pyridyl and tolyl groups of 27.1° in the Ir(III) complex [Ir(ttpyeneanisole)(2)]·3PF(6) is more acute than in the Ru(II) derivative [Ru(tpystilbene)(2)]·2PF(6) (35.5°), indicating the presence of a greater degree of π-delocalisation across the terpyridine unit in the former compound. Their luminescence properties in fluid solution have been investigated following both resonant and non-resonant excitation. We have shown that each of the complexes undergoes two-photon excitation when excited in the near infrared (740 to 820 nm), with two-photon absorption cross sections in the range 11-67 × 10(-50) cm(4) s photon(-1). The larger cross sections for the Ir(III) complexes reflect the differences observed in the solid state. This work therefore demonstrates that such complexes are promising as luminescent markers for 3D imaging and illustrates that simple functionalisation of the chromophores and the choice of metal can lead to marked enhancements in the two-photon cross sections (σ(2)) compared to those of simpler heteroleptic polypyridyl based derivatives.     

Cyclometalated ruthenium chloro and nitrosyl complexes

The novel cyclometalated Ru(III) complex, [Ru(eta(2)-phpy)(trpy)Cl][PF(6)].toluene 1, and the [Ru-NO](6) complex, [Ru(eta(2)-phpy)(trpy)NO][PF(6)](2) 2, where trpy is 2,2': 6',2'-terpyridine and phpy is 2-phenylpyridine, have been prepared and characterized by elemental analysis, IR, (1)H NMR, and electronic absorption spectroscopies, cyclic voltammetry, and crystallography. The crystal structure of 1 showed the chloride ion trans to the sigma-bonding phenyl group of phpy and is an unusual example of a stable paramagnetic cyclometalated complex. The crystal structure of 2 shows the nitrosyl ligand trans to the sigma-bonding phenyl group of phpy. The significant distortion of the normally linear Ru-NO bond angle (167.1(4) degrees) can be largely ascribed to the strong sigma-donor properties of the phenyl group.