Two Bisupporting Keggin-Type POM-Based Hybrids Decorated by [Zn(phen)2]2+ Fragments

On the preferences of five-membered chelate rings in coordination chemistry: insights from the Cambridge Structural Database and theoretical calculations

The purpose of this review is to give an overview of three important N-bidentate ligands: 1,10-phenanthroline (phen), 2,2'-bipyridine (bpy), and ethylenediamine (en). We have not attempted to be comprehensive because of the huge amount of activity being done in coordination chemistry using these ligands. Instead we present a full structural and geometrical study by using the Cambridge Structural Database (CSD) combined with theoretical calculations that allow us to parameterize their coordinating properties and ability to coordinate to transition and non-transition metals. More importantly, we illustrate that upon coordination and formation of the five-membered chelate ring, these ligands are able to adapt themselves to the requirements of the different metals by changing the MN distances and NMN angles. Therefore, a redefinition of the preferences of these ligands to metals with large ionic radii is needed. Finally, we will present some facts about the participation of these ligands in inorganic-organic hybrids (IOHs) based on Keggin polyoxometalates (POMs).

Visible-Light-Driven "On"/"Off" Photochromism of a Polyoxometalate Diarylethene Coordination Complex

Herein we report the first photochromic polyoxometalate (POM)-based diarylethene (DAE) coordination complex, prepared by ligation of two cobalt(III)-incorporated borotungstates [B^IIIW^VI₁₁O₃₉Co^III]^6- with the ditopic pyridyl-containing diarylethene (C₂₅H₁₆N₂F₆S₂). The solution-state composition, structure, and stability of the assembly were probed using ¹H and ¹⁹F nuclear magnetic resonance spectroscopy (NMR), electrospray ionization quadrupolar time-of-flight mass spectrometry (ESI-QTOF-MS), ultraviolet-visible spectroscopy (UV-vis), and small-angle X-ray scattering (SAXS), revealing that the complex self-organizes to adopt a molecular dumbbell structure due to electrostatic and steric considerations. This conformation is a prerequisite for the photocyclization reaction. The assembly was found to be switchable between two states using visible light due to the perturbation of the DAE electronic structure on coordination to the POM. We present photophysical data, including the reaction quantum efficiency of the molecular switch in both directions measured using a custom-built quantum yield determination setup in addition to fatigue resistance on prolonged irradiation.

Hydrothermal synthesis and crystal structure of a bisupporting Keggin-polyoxometalate hybrid compound decorated with a copper(II) complex unit

A bisupporting Keggin-type polyoxometalate compound, {[CuII(phen)2]2[(HBW12O40)]}[CuIICl2(phen)]2· 2H2O (phen=1,10-phenathroline) (1), has been synthesized through the hydrothermal method and characterized by IR spectroscopy, elemental analysis, UV/Vis/NIR spectroscopy, and powder and single crystal X-ray diffraction. The bisupporting Keggin-polyoxometalate consists of one Keggin-type [HBW12O40]4−core and two covalently linked copper(II) complex fragments [Cu(phen)2]2+. In the crystal structure π···π interactions, C–H···Cl, O–H···Cl, O–H···O and C–H···O hydrogen bonds lead to a three-dimensional supramolecular structure.