Dimensional Structures and Electrocatalytic Activities of Platinum(II)-Palladium(II)-Manganese(II) Coordination Polymers Controlled by Chloride versus Bromide

In Situ Conversion of Ligand to a Coordination Polymer via a Core@Shell Crystal: A Multi-Step Phase-Dependent Structural Transformation

Two pseudopolymorphic 1D coordination polymers of the formulas [Cd(3,3'-pytz)(CH3OH)2(ClO4)2]n (1) and [Cd(3,3'-pytz)(CH3CN)2(ClO4)2]n (2) have been prepared using the electron-deficient 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3'-pytz) ligand and cadmium perchlorate in the chloroform/methanol and chloroform/acetonitrile solvent system, respectively. It was observed that compounds 1 and 2 experienced one-step (CPreagent → CPproduct) single-crystal-to-powder structural transformation to the pure water-coordinated compound [Cd(3,3'-pytz)(H2O)2(ClO4)2]n (3) by absorbing water vapor from air (solid-gas phase transformation). Interestingly, compounds 1, 2, and 3 undergo a different transformation path and show an in situ unique three-step (CPreagent → CPproduct → Ligandintermediate → CPproduct) single-crystal-to-single-crystal (SCSC) structural transformation process through soaking in deionized water (solid-liquid phase transformation). In this fascinating transformation, we report for the first time the direct conversion of a ligand into a coordination polymer by a rare core-shell pathway in a solid-liquid phase transformation. In this process, we obtained compound {[Cd(3,3'-pytz)(H2O)4](3,3'-pytz)2(ClO4)2(H2O)6}n (4) (single-crystal = S, crystal = C, or microcrystal = P) as mixed compounds of core-shell L@4C and 4S or core-shell L@4P and 4P for compounds (1 and 2) and 3, respectively.

A chromotropic PtIIPdIICoII coordination polymer with dual electrocatalytic activity for water reduction and oxidation

Here, we present a heterometallic coordination polymer that exhibits heterogeneous electrocatalytic activities for both water reduction and water oxidation. Treatment of the PtII2PdII2 tetranuclear complex [Pd₂{Pt(NH₃)₂(D-pen)₂}₂] ([1]; D-H₂pen = D-penicillamine) with CoX₂ (X = Cl, Br) provided (PtII2PdII2CoII2)_n coordination polymers [Co₂(H₂O)₆(1)]X₄ ([2]X₄), in which the PtII2PdII2 units of [1] are linked by [Co₂(μ-H₂O)(H₂O)₅]⁴⁺ moieties in a 3D network structure. [2]X₄ showed a colour change from orange to dark green upon dehydration, reflecting the geometrical conversion of the Co^II centres in [Co₂(μ-H₂O)(H₂O)₅]⁴⁺ from an octahedron to a tetrahedron by the removal of aqua ligands. While both [2]Cl₄ and [2]Br₄ electrochemically catalysed water reduction to H₂ in the solid state due to the presence of Pd^II active centres, water oxidation to O₂ was catalysed only by [2]Br₄, which is ascribed to the presence of Br^- ions that mediate the catalytic reactions that occurred at Co^II active centres.

Heterometallic coordination polymers as heterogeneous electrocatalysts

Heterometallic coordination polymers have been rapidly developed as heterogeneous electrocatalysts. This review highlights the synthesis strategies of these polymers and the relationships between structures and electrocatalytic performances.