Control of On–Off or Off–On Fluorescent and Optical [Cu2+] and [Hg2+] Responses via Formal Me/H Substitution in Fully Characterized Thienyl “Scorpionate”-like BODIPY Systems

A systematic series of fluorescence chemosensors with multiple binding sites for Hg(ii) based on pyrenyl-functionalized cyclotriphosphazenes and their application in live cell imaging

A systematic series of fluorescence chemosensors based on cyclotriphosphazene derivatives were designed, synthesized, and evaluated for their sensing behaviors toward metal ions.

Ferrocene catalysed heteroarylation of BODIPy and reaction mechanism studies by EPR and DFT methods

Spin cross-over experiment using EPR and DFT calculations show the radical formation.

A Highly Selective Fluorescent Indicator for Copper Based on a Boron Complex

Condensation of 4-(diethylamino)salicylaldehyde with aqueous hydrazine, followed by complexation with BF3·OEt2 gives a fluorescent indicator highly selective for copper. The indicator forms a 2 : 1 complex with Cu2+ and displays a highly sensitive and selective fluorescent quenching action with Cu2+ upon excitation at 440 nm in water/THF (7 : 3, v/v) solution. This action is pH-independent over the range 4.5 < pH < 9.5.

Switching of the triplet excited state of rhodamine/naphthaleneimide dyads: an experimental and theoretical study

Rhodamine-bromonaphthaleneimide (RB-NI) and rhodamine-bromonaphthalenediimide (RB-NDI) dyads were prepared for switching of the triplet excited states. Bromo-NI or bromo-NDI parts in the dyads are the spin converters, i.e., the triplet state producing modules, whereas the RB unit is the acid-activatable electron donor/energy acceptor. NI and NDI absorb at 359 and 541 nm, and the T1 state energy levels are 2.25 and 1.64 eV, respectively. RB undertakes the reversible spirolactam (RB-c) ↔ opened amide (RB-o) transformation. RB-c shows no visible light absorption, and the triplet-state energy level is ET1 = 3.36 eV. Conversely RB-o shows strong absorption at 557 nm, and ET1 is 1.73 eV. Thus, the acid-activated fluorescence-resonance-energy-transfer (FRET) competes with the ISC of NI or NDI. No triplet state was observed for the dyads with nanosecond time-resolved transient absorption spectroscopy. Upon addition of acid, strong fluorescence and long-living triplet excited states were observed. Thus, the producing of triplet state is acid-activatable. The triplet state of RB-NI is localized on RB-o part, whereas in RB-NDI the triplet state is delocalized on both the NDI and RB-o units. The ISC of spin converter was not outcompeted by RET. These studies are useful for switching of triplet excited state.

Fluorometric sensing of Hg2+ ions in aqueous medium by nano-aggregates of a tripodal receptor

Two new tripodal receptors (1–2) have been synthesized and characterized by various spectroscopic techniques. The nano-aggregates of 1 and 2 (N1 and N2) have been prepared by a re-precipitation method in aqueous medium and have shown different photo-physical properties. Nano-aggregates of 1 (N1) can selectively recognize Hg(2+) in aqueous medium in the presence of other metal ions with enhancement in fluorescent intensity. The response was linearly proportional to the concentration of Hg(2+) in the range 0–10 μM with a detection limit of 2.4 nM. The mechanism of selective binding of Hg(2+) by N1 has also been supported by theoretical studies. To the best of our knowledge, this work represents the first report on substituted thiourea based nano-aggregates for nano-molar detection of mercury in aqueous medium.