Triphenylene-Bridged Trinuclear Complexes of Cu: Models for Spin Interactions in Two-Dimensional Electrically Conductive Metal–Organic Frameworks

Abstract

Me 3 tacn)] 2+ (Me 3 tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) produces trigonal tricopper complexes [(Me 3 tacnCu) 3 (HOTP)] 3+ (1) and [(Me 3 tacnCu) 3 (HITP)] 4+ (2) (HOTP, HITP = hexaoxy-and hexaimino-triphenylene, respectively). These trinuclear complexes are molecular models for spin exchange interactions in the two-dimensional conductive metal-organic frameworks (MOFs) copper hexaoxytriphenylene (Cu 3 HOTP 2) and copper hexaiminotriphenylene (Cu 3 HITP 2). Whereas complex 1 is isolated with HOTP 3bearing the same oxidation state as found in the oxy-bridged MOF, the triply oxidized HITP 3found in Cu 3 HITP 2 is unstable with respect to disproportionation in the molecular model. Indeed, magnetic measurements reveal ligandcentered radical character for 1 and a closed-shell structure for 2, in agreement with the redox state of the ligands. All neighboring spins are antiferromagnetically coupled in 1 and 2. These results help probe metal-ligand-metal interactions in conductive MOFs and provide potential inspiration for the synthesis of other two-dimensional materials with delocalized electrons. Figure 1. (a) Structural and chemical representation of typical 2D conductive MOFs, with depiction of the graphite-like honeycomb structure as well as HXTP (X = O, I) ligand-centered radical. The highlighted part illustrates the trinuclear metalligand monomeric unit modeled here as shown in (b). (c) Spin lattice of typical 2D conductive MOFs, with arrows showing randomized spin centers. (d) Spin structure of the monomeric unit depicted in (b), showing metal-and ligand-centered radicals.

Probing Isoreticular Expansions in Phosphonate MOFs and their Applications

“…The systematic synthesis of microporous metal organic frameworks (MOFs) has spawned wide interest in early 2000s for their gas storage properties and sequestration of greenhouse gases , . As MOF research kept growing, distinct applications in diverse fields, such as catalysis, gas adsorption, drug delivery, food transportation, solar cells, conductivity, proton conductivity, biomimetic chemistry, magnetism etc., have emerged . The limitless linker geometries, possibility of attaching reactive organic functional groups around linker scaffolds have created new chemistry namely post synthetic modifications to further optimize the MOF properties .…”

Unpaired 3d Electrons on Atomically Dispersed Cobalt Centres in Coordination Polymers Regulate both Oxygen Reduction Reaction (ORR) Activity and Selectivity for Use in Zinc–Air Batteries

“…This observation suggests a preferential coordination of the HITP ligand with Ni 2+ in comparison to Co 2+ , which can be understood from the following interpretation based on the ligand‐field theory . In Ni 3 HITP 2 , the square‐planar coordination of Ni 2+ results in a D 4 h symmetry with both 3d xy and 3d z 2 orbitals fully filled by paired electrons, leaving the empty and antibonding orbital to coordinate with four primary amines from the ligands (see the top schematic diagram in Figure a) . By contrast, such symmetry is broken in Co 3 HITP 2 due to the last unpaired electron of 3d 7 and the Jahn–Teller effect typically associated with Co 2+ .…”

“…Accordingly,t he samples with Co/Ni feeding ratios of 3/1, 1/1, and 1/3 were denoted as Co 2.14 Ni 0.86 HITP 2 ,C o 1.27 Ni 1.73 HITP 2 ,a nd Co 0.73 Ni 2.27 HITP 2 , respectively.T his observation suggests ap referential coordination of the HITP ligand with Ni 2+ in comparison to Co 2+ , which can be understood from the following interpretation based on the ligand-field theory. [14] In Ni 3 HITP 2 ,t he squareplanar coordination of Ni 2+ results in a D 4h symmetry with both 3d xy and 3d z 2 orbitals fully filled by paired electrons, leaving the empty and antibonding d x 2 Ày 2 orbital to coordinate with four primary amines from the ligands (see the top schematic diagram in Figure 1a). [11a, 14a, 15] By contrast, such symmetry is broken in Co 3 HITP 2 due to the last unpaired electron of 3d 7 and the Jahn-Teller effect typically associated with Co 2+ .Instead of the perfect square-planar coordination, adistorted quadrilateral configuration is taken by Co 3 HITP 2 , resulting in am ixed symmetry of D 4h and O h (note that D 4h can be also regarded as an extreme case of z-axial elongated O h ), and more likely being C 4v .…”

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

“…As a member of the famous 2D conductive CPs, [(Me 3 tacnCu) 3 (HOTP)] 3 + complexes show multi redox peaks in a CV curve. [66] Therefore, designing mixed-valence CPs with redox ligand is a possible strategy.…”