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 HOTP3– bearing the same oxidation state as found in the
oxy-bridged MOF, the triply oxidized HITP3– 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.