Conjugated Metal–Organic Macrocycles: Synthesis, Characterization, and Electrical Conductivity

Abstract

The dimensional reduction of solids into smaller fragments provides a route to achieve new physical properties and gain deeper insight into the extended parent structures. Here, we report the synthesis of CuTOTP-OR (TOTP n− = 2,3,6,7tetraoxidotriphenylene), a family of copper-based macrocycles that resemble truncated fragments of the conductive twodimensional (2D) metal−organic framework Cu 3 (HHTP) 2 (HHTP = 2,3,6,7,10,. The planar metal−organic macrocycles self-assemble into ordered nanotubes with internal diameters of ∼2 nm and short interlayer distances of ∼3.20 Å. Strong π−π stacking interactions between macrocycles facilitate out-of-plane charge transport, and pressed pellet conductivities as high as 2(1) × 10 −3 S cm −1 are observed. Peripheral alkyl functionalization enhances solution processability and enables the fabrication of thin-film field-effect transistor devices. Ambipolar charge transport is observed, suggesting that similar behavior may be operative in Cu 3 (HHTP) 2 . By coupling the attractive features of metal−organic frameworks with greater processability, these macrocycles enable facile device integration and a more nuanced understanding of out-of-plane charge transport in 2D conductive metal−organic frameworks.

Dense Conductive Metal–Organic Frameworks as Robust Electrocatalysts for Biosensing

“…Besides, the strong characteristic peaks at about 1450 cm −1 in all cMOF samples correspond to a metal−semiquinone stretch, which is an intermediate state between the metal−quinone and catecholate complexes. 37 The intense band at ∼365 nm (intraligand π−π* transition) and the broader band at ∼640 nm (ligand-to-metal charge-transfer band) in the UV/vis spectra (Figure 1f) also correspond to a semiquinone assignment. 13,38,39 The ligand-to-metal charge-transfer tran-sition enables cMOFs to have the ability to conduct electricity at room temperature.…”

Cu(I)/Cu(II) Creutz-Taube Mixed-Valence 2D Coordination Polymers

“…The above-discussed spectroscopic characterizations, nonetheless, are unable to distinguish whether a Cu ion is Cu(I) or Cu(II) in the structures. In this case, GCPs 1 and 2 can be classified as Class III mixed-valence structures, [29][30] i.e., Creutz-Taube structures, according to the Robin-Day classification. 31 More importantly, we addressed a long-standing controversy about the oxidation states of metal ions in such 2D materials, and demonstrated that a periodic atomic structure could host a different number of electrons but remain charge-neutral.…”

Oxidative control over the morphology of Cu3(HHTP)2, a 2D conductive metal–organic framework

“…4 In addition to higher mass transport rates, downsizing bulk MOFs to form colloidally stable nanocrystals may also provide important processability advantages. 5,6 This study focuses on controlling the morphology of Cu 3 (-HHTP) 2 (HHTP ¼ 2,3,6,7,10,11-hexahydroxytriphenylene), a prototypical 2D conductive metal-organic framework (Fig. 1).…”

“…4 In addition to higher mass transport rates, downsizing bulk MOFs to form colloidally stable nanocrystals may also provide important processability advantages. 5,6…”