We report on the heterobimetallic complexes {Cu + -Co 3+ -Cu + } (3), {Cu + -Fe 3+ -Cu + } (4), {Cu 2+ -Co 3+ -Cu 2+ } (5), and {Cu 2+ -Fe 3+ -Cu 2+ } (6) and show their catalytic applications in the oxidation of hindered phenols and the oxidative coupling of terminal alkynes. The former reaction produces C-C-coupled and dealkylated products, whereas the latter leads to [a] 2113 the homo-and heterocoupling of terminal alkynes. The facile redox interconversion between Cu + and Cu 2+ for the secondary metal ions in these heterobimetallic complexes appears to be essential for the observed catalysis, and an important design aspect is better substrate accessibility and the use of molecular oxygen as the sole oxidant.portant classes of compounds. [6] Interestingly, both these reactions are oxidative in nature and the presence of a redoxactive metal facilitates the transformation. [7] Therefore it is important to design catalysts that provide redox-active metals with better substrate accessibility and transformation ability. In this context, metalloligands 1 and 2 have been shown to accommodate a variety of secondary metal ions while maintaining substrate accessibility. [3] Importantly, Lewis acidic secondary metal ions in the resultant heterobimetallic complexes and networks facilitate Beckmann rearrangement, ring-opening, and cyanation reactions, [3] whereas the presence of Cu I ions with accessible Cu 2+/+ red-Scheme 1. Metalloligands and heterobimetallic complexes discussed in this work. Crystal StructureHeterobimetallic complexes 5 and 6 are isostructural, however, one of the representative complexes, compound 5, was crystallographically characterized. [11] Complex 5 crystallizes in a triclinic cell system with the P1 space group. A thermal ellipsoidal representation of complex 5 is shown in

This work reports three heterometallic coordination polymers (HCPs), namely, [{(1′) 2 Zn 8 Na 24), originated from a common Co 3+ based metalloligand 1 offering eight arylcarboxylic acid groups where 1′ and 1″ respectively contribute eight and six anionic carboxylate groups. The crystal structure analyses display three-dimensional nature of all three HCPs wherein metalloligands are connected through secondary metals. Detailed topological analyses illustrate that the metalloligands function as the nodes that are connected to secondary building units (SBUs) composed of Zn 2+ , Cd 2+ , and Mn 2+ ions coordinated by the arylcarboxylate groups. All three HCPs effectively function as the heterogeneous catalysts for the Lewis acid assisted Knoevenagel condensation reactions of assorted aldehydes with three different active methylene compounds.

The decrease in photoluminescence (PL) of four different sized CdSe colloidal quantum dots (donors) has been investigated in the presence of three different Cobalt(III) complexes (acceptors). The steady-state and time-resolved PL (TRPL) spectroscopy have been used to investigate the mechanism of quenching. The complex concentration driven change in lifetimes of QDs and stronger PL quenching than predicted solely by TRPL data indicate that the quenching is neither purely static nor purely dynamic in nature. Further, the absence of any ground state complex absorption feature suggests that the static quenching contribution is due to the close proximity of the QDs fluorophores and deactivating sites of complexes. The dynamic quenching processes like diffusion mediated collisional quenching, Dexter energy transfer, and hole transfer have been methodically ruled out, leaving Forster resonant energy transfer (FRET) and the electron transfer (eT) between the QDs and complexes as the possible mechanisms. The Marcus model of eT has been successfully used to demonstrate the otherwise looking random trends of experimental eT rates. The apparent static contributions have been separated from the total quenching by normalization of steady state PL with TRPL data. Finally, FRET and eT mediated dynamic quenching in conjunction with the donor−acceptor proximity driven static quenching was used to explain steady state PL quenching trends.

This work presents synthesis and characterization of trinuclear {Co(2+)-Co(3+)-Co(2+)} and {Co(2+)-Fe(3+)-Co(2+)} complexes with accessible peripheral Co(ii) ions. Both trinuclear complexes function as efficient reusable heterogeneous catalysts for the selective reduction of assorted nitro compounds to the corresponding amines. The mechanistic investigations suggest the involvement of a Co(ii)-Co(i) cycle in the catalysis.

This work presents the synthesis of {Co 3+ -Zn 2+ } and {Co 3+ -Cd 2+ } heterometallic coordination networks. These networks are originated from two unique Co 3+ -based metalloligands containing appended arylcarboxylic acid groups at the strategically placed positions. Such appended arylcarboxylate groups coordinate the secondary metal ions, Zn 2+ and Cd 2+ , to afford distinct three-dimensional networks. All four networks display orderly arrangement of secondary metal ions and unique network topologies including an unprecedented one. These networks have been shown to act as the heterogeneous and reusable catalysts for the Knoevenagel condensation reactions and cyanation reactions of assorted aldehydes. Cyanation reactions nicely demonstrate the substrate size-exclusion catalysis.