A novel fully water-soluble Cu(i) probe for fluorescence live cell imagingElectronic supplementary information (ESI) available: Experimental details of synthetic procedures, characterization and cell cultures; fluorescence titrations, DOSY experiments, confocal image analysis. See DOI: 10.1039/c4cc02147a

A new Cu( i ) probe ( OBEP-CS1 ), bearing an alkyl-pyridinium moiety to get complete water solubility, was synthesized. Fluorescence titrations support copper binding and high selectivity in a water solution whereas formation of aggregates was excluded by DOSY experiments. The detection capability for intracellular Cu( i ), especially localized in mitochondria, was demonstrated in differentiated neuroblastoma cells by confocal microscopy. Monovalent copper detection in solution and in living cells by a new probe is shown. Total water solubility, localization in mitochondria and negligible toxicity of OBEP-CS1 make it suitable for in vitro measurements.