A Triphenylphosphonium-Functionalised Cyclometalated Platinum(II) Complex as a Nucleolus-Specific Two-Photon Molecular Dye

• Published in: Chemistry : a European journal Vol. 16; no. 13; pp. 3942 - 3950
• Main Authors: Koo, Chi-Kin, So, Leo K.-Y., Wong, Ka-Leung, Ho, Yu-Man, Lam, Yun-Wah, Lam, Michael H.-W., Cheah, Kwok-Wai, Cheng, Chopen Chan-Wut, Kwok, Wai-Ming
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 06.04.2010; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Affinity; Animals; Binding Sites; Cell Line, Tumor - chemistry; Cell Line, Tumor - metabolism; Cell Nucleolus - chemistry; Chemistry; Chemistry, Multidisciplinary; Confocal; Excitation; Fluorescent Dyes - chemistry; HeLa Cells - chemistry; HeLa Cells - metabolism; Humans; imaging agents; Lasers; Ligands; Luminescence; Mice; Microscopy, Confocal - methods; Models, Molecular; Molecular Structure; Nuclear Proteins - chemistry; Nuclear Proteins - metabolism; Optical properties; optical tissue sectioning; organelle-specific labeling; Organelles - chemistry; Organelles - metabolism; Organoplatinum Compounds - chemical synthesis; Organoplatinum Compounds - chemistry; Organoplatinum Compounds - toxicity; Photons; Physical Sciences; Platinum; Proteins; Science & Technology; Solutions - chemistry; Temperature; Terminals; two-photon imaging; POLYPYRIDINE COMPLEXES; COORDINATION CHEMISTRY; RECOGNITION; organelle-specific labeling; MITOCHONDRIA; optical tissue sectioning; imaging agents; PROBES; platinum; two-photon imaging; LUMINESCENCE; EXCITATION CROSS-SECTIONS; ABSORPTION; LIGAND; EMISSION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200902919

An organometallic cyclometalated platinum(II) complex, [Pt(L3)Cl][PF6], has been synthesised from a specially designed cyclometalating ligand, HL3 (triphenyl{5‐[3‐(6‐phenylpyridin‐2‐yl)‐1H‐pyrazol‐1‐yl]pentyl}phosphonium chloride), that contains a pendant carbon chain carrying a terminal cationic triphenylphosphonium moiety. Aside from its room temperature single‐photon luminescent properties in solution, [Pt(L3)Cl]+ can also produce two‐photon‐induced luminescence at room temperature upon excitation at 700 nm from a mode‐locked Ti:sapphire laser. Its two‐photon absorption cross‐section in DMF at room temperature was measured to be 28.0×10−50 cm4 s photon−1. [Pt(L3)Cl]+ is able to selectively stain the cell nucleolus. This has been demonstrated by two‐photon confocal imaging of live and methanol‐fixed HeLa (human cervical carcinoma) and 3T3 (mouse skin fibroblasts) cells. This organelle specificity is likely to be related to its special affinity for proteins within cell nucleoli. As a result of such protein affinity, [Pt(L3)Cl]+ is an efficient RNA transcription inhibitor and shows rather profound cytotoxicity. On the other hand, the organelle‐specific labelling and two‐photon‐induced luminescent properties of [Pt(L3)Cl]+ renders it a useful nuclear dye for the 3‐dimensional reconstruction of optical sections of thick tissues, for example, mouse ileum tissues, by multiphoton confocal microscopy. In a flash! A cyclometalated PtII complex has been synthesised from a specially designed cyclometalating ligand with a terminal triphenylphosphonium moiety. The complex exhibits two‐photon‐induced luminescence upon excitation at 700 nm from a Ti:sapphire laser and is able to selectively label the cell nucleolus (see arrows in scheme).