Luminescent lanthanide complexes have fascinating optical properties which make them largely technological used in lighting devices (luminescent lamps, emitting diodes), optical ibres and ampliiers, television and computer displays, lasers, in luoroimmunoassay and luorescence microscopy. Recently there has developed interest in the photophysical properties of lanthanide complexes which are luminescent in the near-IR region, such as Pr(III), Nd(III), Yb(III) and Er(III), in their potential for medical applications, in particular for cancer detection. Unfortunately, lanthanide ions themselves do not absorb light effectively because the relevant f-f transitions are theoretically forbidden. This often means that they require to be bound to a sensitising molecule (organic ligands or transition metal complexes) in order for them to be effectively used as luminescent probes. The cyanometallate anion [Ru(diimine)(CN)4]2- is a promising candidate for use as a d-block component, which has superior photophysical properties and four cyanide groups capable of coordinating to lanthanide [1,2]. A new series of coordination oligomers and polymers in which the tetracyanometallate [Ru(phen)(CN)4]2anions (where phen = 2,2’-phenanthroline) were crystallized with lanthanide(III) cations and phen or trpy diimine ligands (trpy = 2,2′:6′,2′′-terpyridine) has been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray crystallography. Depending on the condition employed and the nature of diimine ligands used a wide variety of topologies of polynuclear species was observed: the two-dimensional grid coordination polymers {[Ru(phen)(CN)4]3[Ln(phen)(H2O)3]}2 ∙ 7H2O}n (Ln = Nd3+, Er3+ (Fig. 1), Yb3+), the hexanuclear clusters {[Ru(phen)(CN)4]2[Ln(phen)2(H2O)] [K(H2O)14]}2 (Ln = Nd3+, Er3+, Yb3+ (Fig. 2)), the ladder chain coordination polymers {[Ru(phen) (CN)4]3[Ln(trpy)(H2O)3]}2 ∙ 12.5H2O}n (Ln = Pr3+ (Fig. 3), Nd3+), and the one-dimensional chain coordination polymers {[Ru(phen)(CN)4]3[Ln(trpy)(H2O)4]}2∙20H2O}n (Ln = Pr3+, Nd3+). The photophysical properties of the synthesized compounds and the structure/property relationship will be discussed. The results will provide an in-depth understanding of the detailed interactions in these new species and will be a major step forward in the rational design of new near-infrared luminescent molecules and solid-state materials, for use in applications as diverse biological sensing and optoelectronic devices.figureFig. 1. A view of a 2D grid structure in {[Ru(phen)(CN)4]3 [Er(phen)(H2O)3]}2 ∙7H2O}nfigureFig. 2. A view of the hexanuclear anionic cluster present in {[Ru(phen)(CN)4]2 [Yb(phen)2(H2O)][K(H2O)14]}2figureFig. 3. A view of the ladder chain of {[Ru(phen)(CN)4]3 [Pr(trpy)(H2O)3]}2∙20H2O}n