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The spectroscopic properties are examined of 1-phenyl-3-benzothiazol-2-yl-5-(4-R-phenyl)-delta(super 2)-pyrazolines, which are strongly dependent on both the electronic nature of the substituent R and solvent polarity. In conclusion, the rigid 'pseudo spiro' geometry of the molecules holds the three substituents of the central delta(super 2)-pyrazoline ring in a fixed prearrangement, which is confirmed by X-ray structure analysis.

The response to Fe(super III) and potentially interfering metal ions is studied in highly polar aprotic and protic solvents for both probes as well as in neat and buffered aqueous solution for one of the sensor molecules, the boron-dipyrromethane (BDP) derivative. The unbound BDP derivative shows dual emission in water and can be employed for the selective ratiometric signaling of Fe(super III) in buffered aqueous solutions.

A general framework for combining two complementary and competitive signaling mechanisms in different metal ions is described.

Issues concerning the fluorescence efficiencies of chalcones with various bridged bonds and different donors and acceptors are discussed. The need to consider at least four photophysically active states is highlighted.

Incorporation of a tailor-made size-restricted dithia-aza-oxa macrocycle, 1-oxa-4,10-dithia-7-aza-cyclododecane, via a phenyl linker into two fluorescent sensor molecules with electronically decoupled, rigidly fixed, and sterically preoriented architectures, a 1,3,5-triaryl-Δ²-pyrazoline and a meso-substituted boron-dipyrromethene (BDP), yields amplified fluorescence in the red-visible spectral range upon binding of FeIII ions. The response to FeIII and potentially interfering metal ions is studied in highly polar aprotic and protic solvents for both probes as well as in neat and buffered aqueous solution for one of the sensor molecules, the BDP derivative. In organic solvents, the fluorescence of both indicators is quenched by an intramolecular charge or electron transfer in the excited state and coordination of FeIII leads to a revival of their fluorescence without pronounced spectral shifts. Most remarkably, the unbound BDP derivative shows dual emission in water and can be employed for the selective ratiometric signaling of FeIII in buffered aqueous solutions. [ABSTRACT FROM AUTHOR]

A bisamidopyridine-type receptor, N , N ′-bis(6-methyl-2-pyridyl)pyridine-2,6-dicarboxamide (1), and its Co III complex were prepared and their X-ray structures were compared to those of N , N ′-diphenylpyridine-2,6-dicarboxamide (2) and Co III (2) 2 . Introduction of the two additional coordinative groups resulted in second-order interactions between the central ion and the nitrogen atoms of the terminal pyridine moieties in the crystalline state. Solution studies in acetonitrile revealed the importance of these interactions for the ligand's metal ion recognition ability. Whereas 2 only binds to Pb II and Cu II , 1 yields complexes with a majority of the heavy and transition metal ions studied, Co II , Ni II , Cu II , Zn II , Fe III , Fe II , Hg II , and Pb II , respectively. The cation binding properties in solution were investigated by absorption spectroscopy and in the case of 1 -M II/III , the formation of two spectroscopically distinguishable types of complexes was found. Protonation experiments and theoretical considerations helped to gain further insight into possible modes of coordination in solution. [ABSTRACT FROM AUTHOR]