01568nas a2200205 4500008004100000245014000041210006900181260000800250300001600258490000700274520081900281100001801100700001801118700002101136700001901157700002401176700002001200700001701220856012501237 2011 eng d00aPhotoactive RuII-polypyridyl complexes that display sequence selectivity and high-affinity binding to duplex DNA through groove binding0 aPhotoactive RuIIpolypyridyl complexes that display sequence sele cFEB a2089–20980 v173 a

The duplex-DNA binding properties of a nonintercalating polypyridyl ruthenium(II) complex that incorporates a linear extended ligand with a catechol moiety has been probed with a variety of photo- and biophysical techniques. These studies reveal that the complex groove binds to DNA sequences biphasically, and displays binding constants equivalent to those of high-affinity metallointercalators. The complex also displays preferential binding to AT-rich sequences. Changes in the structure of the coordinated catechol ligand and the incorporation of intercalating ancillary ligands into the complex were found to modulate both the optical-binding response and binding parameters of the system, which indicates that the catechol moiety plays a crucial role in the observed enhancement to binding affinities.

1 aGhosh, Amrita1 aDas, Priyadip1 aGill, Martin, R.1 aKar, Prasenjit1 aWalkar, Michael, G.1 aThomas, Jim, A.1 aDas, Amitava uhttps://library.ncl.res.in/content/photoactive-ruii-polypyridyl-complexes-display-sequence-selectivity-and-high-affinity02533nas a2200169 4500008004100000245015500041210006900196260000800265300001400273490000700287520185900294100001902153700001902172700001702191700002602208856012902234 2011 eng d00aPhotophysical properties of ligand localized excited state in ruthenium(ii) polypyridyl complexes: a combined effect of electron donor-acceptor ligand0 aPhotophysical properties of ligand localized excited state in ru cAUG a9765-97730 v403 a

We have synthesized ruthenium(II) polypyridyl complexes (1) Ru(II)(bpy)2(L1), (2) Ru(II)(bpy)2(L2) and (3) Ru(II)(bpy)(L1)(L2), where bpy = 2,2′-bipyridyl, L1 = 4-[2-(4′-methyl-2,2′-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) and L2 = 4-(N,N-dimethylamino-phenyl)-(2,2′-bipyridine) and investigated the intra-ligand charge transfer (ILCT) and ligand–ligand charge transfer (LLCT) states by optical absorption and emission studies. Our studies show that the presence of electron donating –NMe2 functionality in L2 and electron withdrawing catechol fragment in L1 ligands of complex 3 introduces low energy LLCT excited states to aboriginal MLCT states. The superimposed LLCT and MLCT state produces redshift and broadening in the optical absorption spectra of complex 3 in comparison to complexes 1 and 2. The emission quantum yield of complex 3 is observed to be extremely low in comparison to that of complex 1 and 2 at room temperature. This is attributed to quenching of the 3MLCT state by the low-emissive 3LLCT state. The emission due to ligand localized CT state (ILCT and LLCT) of complexes 2 and 3 is revealed at 77 K in the form of a new luminescence band which appeared in the 670–760 nm region. The LLCT excited state of complex 3 is populated either via direct photoexcitation in the LLCT absorption band (350–700 nm) or through internal conversion from the photoexcited 3MLCT (400–600 nm) states. The internal conversion rate is determined by quenching of the 3MLCT state in a time resolved emission study. The internal conversion to LLCT and ILCT excited states are observed to be as fast as ∼200 ps and ∼700 ps for complexes 3 and 2, respectively. The present study illustrates the photophysical property of the ligand localized excited state of newly synthesized heteroleptic ruthenium(II) polypyridyl complexes.

1 aVerma, Sandeep1 aKar, Prasenjit1 aDas, Amitava1 aGhosh, Hirendra, Nath uhttps://library.ncl.res.in/content/photophysical-properties-ligand-localized-excited-state-rutheniumii-polypyridyl-complexes02251nas a2200205 4500008004100000245015200041210006900193260000800262300001400270490000700284520148800291100001901779700002101798700001901819700001401838700001701852700002301869700002401892856012901916 2012 eng d00aPhotosensitization of nanoparticulate TiO2 using a Re(I)-polypyridyl complex: studies on interfacial electron transfer in the ultrafast time domain0 aPhotosensitization of nanoparticulate TiO2 using a ReIpolypyridy cAPR a8192-81980 v143 a

We have synthesized a new photoactive rhenium(I)-complex having a pendant catechol functionality [Re(CO)3Cl(L)] (1) (L is 4-[2-(4′-methyl-2,2′-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) for studying the dynamics of the interfacial electron transfer between nanoparticulate TiO2 and the photoexcited states of this Re(I)-complex using femtosecond transient absorption spectroscopy. Our steady state absorption studies revealed that complex 1 can bind strongly to TiO2 surfaces through the catechol functionality with the formation of a charge transfer (CT) complex, which has been confirmed by the appearance of a new red-shifted CT band. The longer wavelength absorption band for 1, bound to TiO2 through the proposed catecholate functionality, could also be explained based on the DFT calculations. Dynamics of the interfacial electron transfer between 1 and TiO2 nanoparticles was investigated by studying kinetics at various wavelengths in the visible and near infrared regions. Electron injection into the conduction band of the nanoparticulate TiO2 was confirmed by detection of the conduction band electron in TiO2 (Image ID:c2cp24105f-t1.gif) and the cation radical of the adsorbed dye (1˙+) in real time as monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (<100 fs) electron injection was observed. Back electron transfer dynamics was determined by monitoring the decay kinetics of 1˙+ and Image ID:c2cp24105f-t2.gif.

1 aKar, Prasenjit1 aBanerjee, Tanmay1 aVerma, Sandeep1 aSen, Anik1 aDas, Amitava1 aGanguly, Bishwajit1 aGhosh, Hirendra, N. uhttps://library.ncl.res.in/content/photosensitization-nanoparticulate-tio2-using-rei-polypyridyl-complex-studies-interfacial