Search

Excited-state intra-molecular proton transfer (ESIPT)-active imine and azine derivatives, structurally characterised by XRD, and denoted L1, L2, L3 and L4, possess weak fluorescence. The interaction of these probes with Zn 2+ turns ON the fluorescence to allow its nano-molar detection. Among the four ESIPT-active molecules, L2, L3 and L4 are bis-imine derivatives while L1 is a mono-imine derivative. Among the three bis-imine derivatives, one is symmetric (L3) while L2 and L4 are unsymmetrical. The lowest detection limits (DL) of L1, L2, L3 and L4 for Zn 2+ are 32.66 nM, 36.16 nM, 15.20 nM and 33.50 nM respectively. All the probes bind Zn 2+ (10 5 M -1 order) strongly. Computational studies explore the orbital level interactions responsible for the associated photo-physical processes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

An amide-based smart probe (L) is explored for nanomolar detection of Mo(VI) ion in a ratiometric manner, involving hydrogen-bond-assisted chelation-enhanced fluorescence process through inhibition of photoinduced electron transfer process. The recognition of Mo(VI) is associated with a 17-fold fluorescence enhancement and confirmed by single-crystal X-ray diffraction of the resulting Mo(VI) complex (M1). Further, M1 selectively recognizes arsenite through green emission of their adduct (C1) with an 81-fold fluorescence enhancement. Interestingly, dihydrogen phosphate causes dissociation of C1 back to free L having weak fluorescence. The methods are fast, highly selective, and allow their bare eye visualization at physiological pH. All of the interactions have been substantiated by time-dependent density functional theory calculations to rationalize their spectroscopic properties. The corresponding lowest detection limits are 1.5 × 10 -8 M for Mo(VI), 1.2 × 10 -10 M for AsO 2 - , and 3.2 × 10 -6 M for H 2 PO 4 - , whereas the respective association constants are 4.21 × 10 5 M -1 for Mo(VI), 6.49 × 10 4 M -1 for AsO 2 - , and 2.11 × 10 5 M -1 for H 2 PO 4 - . The L is useful for efficient enrichment of Mo(VI) from aqueous solution, while M1 efficiently removes AsO 2 - from environmental samples by solid-phase extraction., Competing Interests: The authors declare no competing financial interest.

A rhodamine-based smart probe ( RHES ) has been developed for trace-level detection and discrimination of multiple cations, viz. Al 3+ , Zn 2+ , Cd 2+ , and Hg 2+ in a ratiometric manner involving photo-induced electron transfer-chelation-enhanced fluorescence-fluorescence resonance energy transfer processes. The method being very fast and highly selective allows their bare eye visualization at a physiological pH. The optimized geometry and spectral properties of RHES and its cation adducts have been analyzed by time-dependent density functional theory calculations. RHES detects as low as 1.5 × 10 -9 M Al 3+ , 1.2 × 10 -9 M Zn 2+ , 6.7 × 10 -9 M Cd 2+ , and 1.7 × 10 -10 M Hg 2+ , whereas the respective association constants are 1.33 × 10 5 M -1 , 2.11 × 10 4 M -1 , 1.35 × 10 5 M -1 , and 4.09 × 10 5 M -1 . The other common ions do not interfere. The probe is useful for intracellular imaging of Zn 2+ , Cd 2+ , and Hg 2+ in squamous epithelial cells. RHES is useful for the determination of the ions in sea fish and real samples., Competing Interests: The authors declare no competing financial interest.