A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. The linkage isomers {(C4H9)4N}3[Ru(Htcterpy)(–NCS)3] 1, {(C4H9)4N}3[Ru(Htcterpy)(–NCS)2(–SCN)] 2 and {(C4H9)4N}3[[Ru(Htcterpy)(–SCN)3] 3 have been separated by pH titration method and fully characterized by UV–Vis, emission, IR and NMR studies. The absorption and emission maxima of the isomer 1 show a bathochromic shift with decreasing pH, and exhibit pH-dependent excited state lifetimes. The red-shift of the emission maxima is due to better π-acceptor properties of the acid form that lowers the energy of the CT excited state. The isomer 1, when anchored to nanocrystalline TiO2 films achieves very efficient sensitization over the whole visible range extending into the near IR region up to 920 nm, yielding over 80% incident photon-to-current conversion efficiencies (IPCEs). Solar cells containing the isomer 1 were subjected to analysis by a photovoltaic calibration laboratory (NREL, USA) to determine their solar to electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm2 and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.