Such as sickle cell anemia [6,7]. Consequently, a great deal of attention has been invested into the development of MedChemExpress BIBS39 luminescent probes for live cell imaging in recent years. Currently, organic dyes constitute the majority of the most commonly-used fluorescent probes [8]. However, organic dyes can be subject to various drawbacks, including small Stokes shift values and short luminescence lifetimes [9?1]. In this context, luminescent transition metal complexes have arisen as viable alternatives to organic fluorophores for sensing and imaging applications due to the following advantages: [12?6] (i) tunable excitation and emission maxima over the visible region without the need for lengthy synthetic protocols; (ii) tunable emission energies by modification of the ancillary ligands; (iii) large Stokes shift for facile separation of excitation and emission wavelengths and elimination of self-quenching; (iv) relatively long phosphorescence lifetimes that can mitigate a short-lived autofluorescence background through the use of timeresolved spectroscopy which offers high selectivity; and (v) good solubility in aqueous solution (containing ,0.01 organic solvent). In eukaryotes, the cytoplasm is an aqueous fluid that primarily consists of a transparent substance termed hyaloplasm or cytosol. Numerous life processes take place within the cytoplasm, including protein synthesis, metabolic reactions, and cellular signaling.However, only a few phosphorescent metal complexes have been developed for cytoplasmic staining. For example, Coogan and coworkers have reported a series of Re(I) complexes of type fac[Re(bisim)L(CO)3]+ containing highly lipophilic esters of 3hydroxymethylpyridine as luminescence agents that selectively distribute in membranes and membrane structures within the cytoplasm of living cells [35]. Barton and co-workers investigated a series of phosphorescent ruthenium(II) complexes with different ancillary ligands that selectively stain the cytoplasm [37]. The CASIN chemical information groups of Li and Lo have developed a series of cationic iridium(III) complexes as phosphorescent probes for luminescence staining of the cytoplasm of living cells [29,38?0]. Iridium(III) complexes with d6 electronic structures often possess excellent photophysical properties such as tunable excitation and emission wavelengths (from blue to red), high luminescent quantum yields, and relatively long phosphorescence lifetimes [41,42]. Iridium complexes have received considerable attention in inorganic photochemistry [43?8], phosphorescent materials for optoelectronics [49?0], chemosensors [61?6], biolabeling[67?9], live cell imaging [29,70?2], and in vivo tumor imaging [73]. As part of our continuous efforts, the cyclometalated iridium(III) solvato complex [Ir(ppy)2(solv)2]+ has been utilized as a selective luminescent switch-on probe for histidine/histidine-rich proteins and a dye for protein staining in sodium dodecyl sulfate polyacrylamide gels [74]. Subsequently, Li and co-workers reported iridium(III) solvato complex [Ir(ppy)2(DMSO)2]+ as a luminescence agent for imaging live cell nuclei [75]. Thus, we were interested to investigate the effect of varying the extent of conjugation of the C N co-ligand on the photophysical properties of this type of complex. We herein report the application of iridium(III) solvato complex [Ir(phq)2(solv)2]+ (1) for the detection`Cell ImagingFigure 1. Chemical structures 1407003 of iridium(III) solvato complexes 1? bearing different C N ligands. doi:10.13.Such as sickle cell anemia [6,7]. Consequently, a great deal of attention has been invested into the development of luminescent probes for live cell imaging in recent years. Currently, organic dyes constitute the majority of the most commonly-used fluorescent probes [8]. However, organic dyes can be subject to various drawbacks, including small Stokes shift values and short luminescence lifetimes [9?1]. In this context, luminescent transition metal complexes have arisen as viable alternatives to organic fluorophores for sensing and imaging applications due to the following advantages: [12?6] (i) tunable excitation and emission maxima over the visible region without the need for lengthy synthetic protocols; (ii) tunable emission energies by modification of the ancillary ligands; (iii) large Stokes shift for facile separation of excitation and emission wavelengths and elimination of self-quenching; (iv) relatively long phosphorescence lifetimes that can mitigate a short-lived autofluorescence background through the use of timeresolved spectroscopy which offers high selectivity; and (v) good solubility in aqueous solution (containing ,0.01 organic solvent). In eukaryotes, the cytoplasm is an aqueous fluid that primarily consists of a transparent substance termed hyaloplasm or cytosol. Numerous life processes take place within the cytoplasm, including protein synthesis, metabolic reactions, and cellular signaling.However, only a few phosphorescent metal complexes have been developed for cytoplasmic staining. For example, Coogan and coworkers have reported a series of Re(I) complexes of type fac[Re(bisim)L(CO)3]+ containing highly lipophilic esters of 3hydroxymethylpyridine as luminescence agents that selectively distribute in membranes and membrane structures within the cytoplasm of living cells [35]. Barton and co-workers investigated a series of phosphorescent ruthenium(II) complexes with different ancillary ligands that selectively stain the cytoplasm [37]. The groups of Li and Lo have developed a series of cationic iridium(III) complexes as phosphorescent probes for luminescence staining of the cytoplasm of living cells [29,38?0]. Iridium(III) complexes with d6 electronic structures often possess excellent photophysical properties such as tunable excitation and emission wavelengths (from blue to red), high luminescent quantum yields, and relatively long phosphorescence lifetimes [41,42]. Iridium complexes have received considerable attention in inorganic photochemistry [43?8], phosphorescent materials for optoelectronics [49?0], chemosensors [61?6], biolabeling[67?9], live cell imaging [29,70?2], and in vivo tumor imaging [73]. As part of our continuous efforts, the cyclometalated iridium(III) solvato complex [Ir(ppy)2(solv)2]+ has been utilized as a selective luminescent switch-on probe for histidine/histidine-rich proteins and a dye for protein staining in sodium dodecyl sulfate polyacrylamide gels [74]. Subsequently, Li and co-workers reported iridium(III) solvato complex [Ir(ppy)2(DMSO)2]+ as a luminescence agent for imaging live cell nuclei [75]. Thus, we were interested to investigate the effect of varying the extent of conjugation of the C N co-ligand on the photophysical properties of this type of complex. We herein report the application of iridium(III) solvato complex [Ir(phq)2(solv)2]+ (1) for the detection`Cell ImagingFigure 1. Chemical structures 1407003 of iridium(III) solvato complexes 1? bearing different C N ligands. doi:10.13.