New platinum(II) terpyridyl acetylide complexes having the ability to bind to TiO2 have been synthesized and assayed in their ability to sensitize platinized titanium dioxide for the photogeneration of H-2 using visible light (lambda > 410 nm). Specifically, the complexes [Pt(tpy-phen-COOH)(C C-C6H5)]Cl (1), where tpy-phen-COOH = 4'-(4-carboxyphenyl)-[2,2';6',2 '']terpyridine and C C-C6H5 = phenylacetylide, and [Pt(tpy-COOH)(C C-C(6)H5())] (2), where tpyCOOH = 4'-carboxy-2,2';6',2"-terpyridine, were prepared to investigate the effectiveness of attachment and proximity to the TiO2 surface on hydrogenyield. Both complexes 1 and 2 sensitize the photogeneration of hydrogen, but produce fewer turnovers than the unbound chromophore, [Pt(ttPY)(C=C_C6H5)]PF6 (5). On the basis of these observations and electrochemical data, a major limitation to the effectiveness of these chromophores is their instability upon oxidation. To attempt to remedy this problem, two donor-chromophore (D-C) dyads, [Pt(tpy-phen-COOH)(C C-C6H4CH2-PTZ)]PF6 (3), where C C-C6H4CH2-PTZ = N-(4-ethynylbenzyl)-phenothiazine and [Pt(tpy-COOH)(C C-C6H4CH2-PTZ)]Cl (4) were prepared to function as TiO2-aftached sensitizers. Transient absorption measurements have shown that the PTZ moiety reductively quenches the Pt center in several picoseconds. While the resultant PTZ(+) radical cation is capable of oxidizing rapidly the triethanolamine sacrificial electron donor, dyads 3 and 4 attached to platinized TiO2 do not function to generate hydrogen upon irradiation, in contrast with results seen for 1 and 2.