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 (MLCT)-M-1 (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 (MLCT)-M-3 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

Structural Investigation in Solution of a series of five-Coordinate Bisphosphinoaryl Ruthenium(II) Complexes

The structure of the ruthenium(II) complexes [RuCl{C6H2(CH2PPh2)2-2,6-R-4}(PPh3)] [R = H (1), Ph (2) or Br (3)] was investigated in solution using two-dimensional NMR techniques (1H-1H-, 13C-1H- and 31P-1H-correlation NMR spectroscopy and 1H NOESY). The 1H and 13C NMR spectra of the complexes 1-3 were similar and could be completely assigned. The results of the NOESY study indicated that these complexes have a distorted square-pyramidal geometry in solution as was established for the parent complex R = H in the solid state by an X-ray crystal structure determination. The strategies used for the interpretation of the 1H, 13C and 31P NMR spectra of these compounds and the resulting assignments form the basis for future in situ studies involving these complexes in catalytic processes. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/2000/99478_s.pdf or from the author

Synthesis and self-assembly of giant porphyrin discs

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