Control of Electronic Structure and Conductivity in Two-Dimensional Metal–Semiquinoid Frameworks of Titanium, Vanadium, and Chromium

Abstract

The isostructural, two-dimensional metal-organic frameworks (HNMe)M(Cldhbq) (M = Ti, V; Cldhbq = deprotonated 2,5-dichloro-3,6-dihydroxybenzoquinone) and (HNMe)Cr(dhbq) (dhbq = deprotonated 2,5-dihydroxybenzoquinone) are synthesized and investigated by spectroscopic, magnetic, and electrochemical methods. The three frameworks exhibit substantial differences in their electronic structures, and the bulk electronic conductivities of these phases correlate with the extent of delocalization observed via UV-vis-NIR and IR spectroscopies. Notably, substantial metal-ligand covalency in the vanadium phase results in the quenching of ligand-based spins, the observation of simultaneous metal- and ligand-based redox processes, and a high electronic conductivity of 0.45 S/cm. A molecular orbital analysis of these materials and a previously reported iron congener suggests that the differences in conductivity can be explained by correlating the metal-ligand energy alignment with the energy of intervalence charge-transfer transitions, which should determine the barrier to charge hopping in the mixed-valence frameworks.

Coupled Electrical Conduction in Coordination Polymers: From Electrons/Ions to Mixed Charge Carriers

“…Later, isostructural two-dimensional frameworks were constructed by dhbq and various metal nodes including Ti, V, Cr. [64] The results imply that the V-based crystal showed a better conductivity of 0.45 S cm À 1 . For all of these frameworks, Li + ions can readily access to the crystal under cyclic voltammograms (CV) cycles.…”

Coordination‐driven self‐assembly of Cp*Rh‐Based Rectangles, Cages and Their Host−Guest Binding Study

“…Then, the solution was concentrated to give a dark red solid 1d, which was washed by diethyl ether and dried under vacuum. If the B 10 H 12 L 2 are reaction with Cp * Rh units got the complex 1 f. (2) 26.4855 (10) 28.5235 (8) 15.4346 (18) b [Å] 32.0893 (7) 11.5806 (15) 20.205 (3) 30.2761 (13) 28.5235 (8) 17.3342 (19)…”

“…[14][15][16][17] Recent work by Fujita, Stang, Nitschke, Clever and others has reported the understanding of the assembly principles with respect to the size, shape, and guest-binding capabilities of such structures. [18][19][20][21][22][23] It is first important to note that the clever use of a series of homologous metallacycles or metallacages derivatives with the aim of finding the ideal match between the size of the anionic guest and the cavity. [24][25][26][27][28][29] The second is for their potential applications.…”

Recent Development and Application of Conductive MOFs

“…The lower conductivity in the Cl‐dbhq framework is likely due to long interlayer distance between adjacent layers (8.7 Å), while in the dbhq framework the conductive path is expanded in three dimensions (Figure ). Recently, Ziebel et al . synthesized a series of isostructural layered hexagonal MOFs with different metal ions (Ti 2+ , V 2+ and Cr 2+ ).…”