Ruthenium–Benzothiadiazole Building Block Derived Dynamic Heterometallic Ru–Ag Coordination Polymer and Its Enhanced Water-Splitting Feature

Abstract

This article deals with the development of the unprecedented redox-mediated heterometallic coordination polymer {[Ru III (acac) 2 (μ-bis-η 1 -N,η 1 -N-BTD) 2 Ag I (ClO 4 )]ClO 4 } n (3) via the oxidation of the monomeric building block cis-[Ru II (acac) 2 (η 1 -N-BTD) 2 ] (1) by AgClO 4 (BTD = exodentate 2,1,3-benzothiadiazole, acac = acetylacetonate). Monomeric cis-[Ru II (acac) 2 (η 1 -N-BTD) 2 ] (1) and [Ru II (acac) 2 (η 1 -N-BTD)-(CH 3 CN)] (2) were simultaneously obtained from the electrondeficient BTD heterocycle and the electron-rich metal precursor Ru II (acac) 2 (CH 3 CN) 2 in refluxing CH 3 CN. Molecular identities of 1−3 were authenticated by their single-crystal X-ray structures as well as by solution spectral features. These results also reflected the elusive trigonal-planar geometry of the Ag ion in Ru−Ag-derived polymeric 3. Ru(III) (S = 1/2)-derived 3 displayed metal-based anisotropic EPR with ⟨g⟩/Δg = 2.12/0.56 and paramagnetically shifted 1 H NMR. Spectroelectrochemistry in combination with DFT/TD-DFT calculations of 1 n and 2 n (n = 1+, 0, 1−) determined a metal-based (Ru II /Ru III ) oxidation and BTD-based reduction (BTD/BTD •− ). The drastic decrease in the emission intensity and quantum yield but insignificant change in the lifetime of 3 with respect to 1 could be addressed in terms of static quenching and/or a paramagnetism-induced phenomenon. A homogeneously dispersed dumbbell-shaped morphology and the particle diameter of 3 were established by microscopic (TEM-EDX/SEM) and DLS analysis, respectively. Moreover, the dynamic nature of polymeric 3 was highlighted by its degradation to the η 1 -N-BTD coordinated monomeric fragment 1, which could also be followed spectrophotometrically in polar protic EtOH. Interestingly, both monomeric 1 and polymeric 3 exhibited efficient electrocatalytic activity toward water oxidation processes (OER, HER) on immobilization on an FTO support, which also divulged the better intrinsic water oxidation activity of 3 in comparison to 1.

Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

“…Unlike {[ 10 ]­(ClO 4 ) 2 } n , the topology of the ligand L2 2– did not allow the structure of [ 11 ]­(ClO 4 ) 2 ([(bpy) 2 Os III -L2 2– -Ag I (CH 3 CN)]­(ClO 4 ) 2 ) (Figure ) to extend along any crystallographic axis and that indeed restricted it to form a heterometallic dimer due to the syn orientation of the N2-coordinated Ag I ion with respect to the O2 atom of the carboxylate function. The average Os III -N­(bpy) ( 10 2+ : 2.063(3)/ 11 2+ :2.058­(6) Å), Ag I -N (L1 2– : 2.132(3)/L2 2– : 2.127(6) Å), and Ag I -N (CH 3 CN: 2.114(4) Å) bond distances matched well with those reported for the analogous systems …”

Chalcogen-bonded donor–acceptor complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4-b]pyrazine with halide ions

“…in complexes with transition metals, due to the lone pairs of nitrogen atoms. [15][16][17][18][19][20] Besides, they possess chalcogen-centered s-holes [21][22][23][24][25][26] capable of secondary bonding interactions (SBIs) 27 /chalcogen bonding (ChB), i.e. are able to act as s-acceptors.…”

Redox-Induced Intramolecular C–C Coupling of Acyclic Bis(2-pyridylmethylene)ethylenediamine on a Ru(acac)2 Platform

“…In agreement with the trans configuration, 3 2+ exhibited one 31 P NMR peak at 45 ppm (Figure S8). On the other hand, DPP-bridged 2 displayed 1 H NMR signals corresponding to the full molecule (10H-DPP, 4CH-acac, and 8CH 3 -acac) . The disappearance of the aldimine (NCH)/methylene (CH 2 –CH 2 ) protons with the concomitant appearance of two new aromatic protons attributed to the transformation of BPE to DPP in 2 .…”

“…20a On the other hand, DPP-bridged 2 displayed 1 H NMR signals corresponding to the full molecule (10H-DPP, 4CH-acac, and 8CH 3 -acac). 21 The disappearance of the aldimine (NCH)/methylene (CH 2 −CH 2 ) protons with the concomitant appearance of two new aromatic protons attributed to the transformation of BPE to DPP in 2. The ν(ClO 4 ) vibrations of [2]ClO 4 and [3](ClO 4 ) 2 appeared at ≈1100 cm −1 (Figure S9).…”