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

Reaction of 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 2,3,6,7,10,11-hexaaminotriphenylene (HATP) with [Cu(Me₃tacn)]²⁺ (Me₃tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane) produces trigonal tricopper complexes [(Me₃tacnCu)₃(HOTP)]³⁺ (1) and [(Me₃tacnCu)₃(HITP)]⁴⁺ (2) (HOTP, HITP = hexaoxy- and hexaiminotriphenylene, respectively). These trinuclear complexes are molecular models for spin exchange interactions in the two-dimensional conductive metal-organic frameworks (MOFs) copper hexaoxytriphenylene (Cu₃HOTP₂) and copper hexaiminotriphenylene (Cu₃HITP₂). Whereas complex 1 is isolated with HOTP^3- bearing the same oxidation state as found in the oxy-bridged MOF, the triply oxidized HITP^3- found in Cu₃HITP₂ is unstable with respect to disproportionation in the molecular model. Indeed, magnetic measurements reveal ligand-centered 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.