We report here the design and synthesis of porphyrin-metallocene dyads consisting of a metallocene [either ferrocene or mixed sandwich η(5)-[C5H4(COOH)]Co(η(4)-C4Ph4) connected via an ester linkage at meso phenyl position of either free-base or zinc porphyrin. All these dyad systems were characterized by various spectroscopic and electrochemical methods. A dimeric form of this molecule was observed in the X-ray crystal structure of Zn-TTPCo. The absorption spectra of all four dyads indicated the absence of electronic interactions between porphyrin macrocycle and metallocene in the ground state. However, interestingly, in all four dyads, fluorescence emission of the porphyrin was quenched (19-55%) as compared to their monomeric units. The quenching was more pronounced in ferrocene derivatives rather than cobaltocenyl derivatives. The emission quenching can be attributed to the excited-state intramolecular photoinduced electron transfer from metallocene to singlet excited state of porphyrin and the electron-transfer rates (k(ET)) were established in the range 1.51 × 10(8) to 1.11 × 10(9) s(-1). They were found to be solvent dependent.

A simple one‐pot synthesis, the characterization, optoelectronic, and cation sensing properties of 1‐(2‐pyridyl)‐3‐ferrocenylpyrazolines 4–6 are described in this article. Reaction of ferrocenyl chalcones with 2‐hydrazinopyridine gave the target compounds in good yield. These compounds were characterized by general spectroscopic techniques and the structure of 4 was determined by means of X‐ray crystallography. These ferrocene compounds behave as selective multichannel chemosensors (redox, chromogenic, and fluorescent) in the presence of Co2+, Cu2+, and Zn2+ ions. The binding assay and recognition ability of these receptors towards the metal ions were explained by electrochemical and optical studies. A maximum cathodic shift in the redox potential of the ferrocenium couple was observed towards the Co2+ ion (ΔE1/2 = 99–156 mV), while a minimum shift was observed with the Zn2+ ion (ΔE1/2 = 72–129 mV) on complexation with these receptors. Disappearance of the high‐energy (HE) band and a red shift (Δλ = 7–13 nm) of the low‐energy (LE) band in the absorption spectra of the receptors 4 and 5 was observed upon complexation with these metal ions. This change in absorption was accompanied by a color change from yellow to red/brown, which enabled potential “naked eye” detection. The emission spectra (λex = 350 nm) of receptor 4, in the presence of these cations, showed a 2–7‐fold increment in the chelation‐enhancement fluorescence (CHEF) and a 4–9‐fold increase in the quantum yield.

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A family of substituted benzimidazolyl-based tripodal molecules with alkyl substituted spacers was synthesized, showing perfect symmetric cyclic aromatic trimer motifs which remained intact in the solid as well as solution state.

A family of biaryl/alkylthiophene (R–R) benzimidazolyl-based tripodal molecules with cyclic benzene trimer (CBT) motif was synthesized and studied by NMR spectroscopy and MPW1PW91/6-311+G(d,p) theory.