Ruthenium Complexes Containing 2,2′-Bipyridine and 1,3,5-Triaza-7-phosphaadamantane

Water‐soluble complexes cis‐[Ru(bpy)2(PTA)2]Cl2 (1Cl2), cis‐[Ru(bpy)2(PTA)2](PF6)2 [1(PF6)2], trans‐[Ru(bpy)2(PTA)2](CF3SO3)2 [2(CF3SO3)2], cis‐[Ru(bpy)2(PTA)(H2O)](CF3SO3)2 [3(CF3SO3)2], cis‐[Ru(bpy)2(PTAH)(H2O)](CF3SO3)3·2CF3SO3H [4(CF3SO3)3·2CF3SO3H], cis‐[Ru(bpy)2(PTAH)2](CF3SO3)4·4CF3SO3H [5(CF3SO3)4·4CF3SO3H], and trans‐[Ru(bpy)2(PTAH)2](CF3SO3)4·4CF3SO3H [6(CF3SO3)4·4CF3SO3H] (bpy = 2,2′‐bipyridyl; PTA = 1,3,5‐triaza‐7‐phosphaadamantane) have been synthesized and characterized by elemental analysis, NMR, and IR spectroscopy. The crystal structures of 1(PF6)2, 2(CF3SO3)2, and 3(CF3SO3)2 were obtained by single‐crystal X‐ray diffraction. Both experimental and computational techniques were utilized to perform a detailed analysis of the structural and electronic properties of complexes 1 and 2 in water in both the deprotonated and protonated state and under N2 and air. Luminescence studies showed that these complexes are active fluorescence compounds, despite the presence of monophosphines in their structure. The pH sensitivity of the emission band of both complexes and their photohydrolysis in acidic water solution was studied. Both complexes release a PTA molecule under selective irradiation in acidic water to give complex 4. Cyclic voltammetry showed that, in water, irreversible anodic oxidation corresponding to the RuII/RuIII redox process occurs for 1, whereas for 2 the process is quasi‐reversible, while in N,N‐dimethylformamide for both complexes they are irreversible and occur at lower potential than in water. New water‐soluble ruthenium complexes containing 1,3,5‐triaza‐7‐phosphaadamantane (PTA) and 2,2′‐bipyridine were characterized, and their optical properties in water were studied. Luminescence studies on these pH‐sensitive complexes showed that they are active fluorescence compounds, despite the presence of monophosphines in their structure.