Keywords: Ruthenium / Tridentate ligands / Bridging ligands / Electron transfer / PhotochemistryFour ditopic bridging ligands, containing 2,2Ј:6Ј,2ЈЈ-terpyridine and 2,6-dipyrazinylpyridine (dpp) metal-binding units attached through p-or m-phenylene linkages, have been incorporated into eight mono-, di-and trinuclear linear Ru II complexes. These were characterized by UV/Vis spectroscopy and cyclic voltammetry, and by their ability to undergo light-induced electron transfers to methylviologen. The dpp-

A new, one-step preparation of 1,4-di(2,2':6',2' '-terpyridin-4'-yl)benzene was employed in the synthesis of a linear trinuclear Ru(II) complex, which was compared to mononuclear and dinuclear analogues using UV-vis spectrometry, cyclic voltammetry, and ability to sensitize the photogeneration of methyl viologen radical cation. The chain length-dependent increase in sensitization ability was consistent with an increasing molar absorbance and with an end-on approach of the photoreactants mitigating the increasing charge.

Key indicatorsSingle-crystal X-ray study T = 150 K Mean '(C±C) = 0.004 A Ê Disorder in solvent or counterion R factor = 0.063 wR factor = 0.175 Data-to-parameter ratio = 12.3For details of how these key indicators were automatically derived from the article, seeThe title compound, 1,3-bis(2,2 H :6 H ,2 HH -terpyridin-4 H -yl)benzene dichloromethane solvate, C 36 H 24 N 6 ÁCH 2 Cl 2 , is a new ligand suitable for bridging two metal centres. Though not in binding conformations, its two terpyridine units are linked in a unique arrangement, through a meta-phenylene core, which disallows resonance communication between binding sites, as re¯ected by the crystal structure of its 1:1 CH 2 Cl 2 solvate. The two terpyridine units are related by crystallographically imposed twofold symmetry, forming a 30.02 (8) dihedral angle with the phenylene core, but with fairly coplanar pyridine rings within. The solvent molecule is disordered over the twofold axis.

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