Treatment of (PPh₄)₂[Ruᴵᴵ(PPh₃)₂(CN)₄] (1) with bpyOH and phenOH in DMF afforded two mononuclear compounds fac-(PPh₄)[Ruᴵᴵ(bpyOH)(PPh₃)(CN)₃] (2) and fac-(PPh₄)[Ruᴵᴵ(phenOH)(PPh₃)(CN)₃] (3), respectively (bpyOH = 6-hydroxy-2,2’-bipyridine; phenOH = 2-hydroxy-1,10-phenanthroline). These complexes have been characterized by various spectroscopic techniques. The structures of 1 and 2 have also been determined by X-ray crystallography. Their photophysical and electrochemical properties have been investigated. Compound 3 displays intense emission with much higher quantum efficiency (Φem = 19.4%) in solution, compared with other related ruthenate(II) diimine complexes. In addition, their solvatochromism, pH effects, and ion perturbation have also been investigated. The different photoluminescent behaviors between these complexes and the previously reported complex [Ruᴵᴵ(phen)(PPh₃)(CN)₃]⁻ suggest that the introduction of the hydroxyl group into the diimine ligand would significantly affect their emission properties. Through spectrophotometric titrations, the ground state pKₐ and excited state pKₐ* values, as well as the dynamic pH response ranges of these complexes have been determined. Their photophysical response towards various metal ions have also been studied. Copyright © 2016 The Royal Society of Chemistry.