Photophysical, ion-sensing and biological properties of rhodamine-containing transition metal complexes

Rhodamine organic dyes have been known for years and have been applied in biological studies because of numerous optical advantages, while rhodamine derivatives with spiro-ring have been investigated as selective and sensitive chemosensors since past two decades. In contrast to the organic fluorophores, most of the luminescence transition metal complexes have been found to exhibit phosphorescence which possesses longer lifetime and large Stokes shift. The hybrid system from the combination of rhodamine organic system and transition metal complexes have been recently explored. This review reports the recent development of rhodamine-containing transition metal complexes. The rhodamine unit in the hybrid system could be classified as latent rhodamine derivatives with sensory ON-OFF properties or with photoactive rhodamine dye as chromophore and fluorophore. The photophysical, ion-sensing and biological studies of various transition metal complexes will be discussed upon attachment of such rhodamine units.