Radical qubits photo-generated in acene-based metal–organic frameworks

Abstract

A series of metal-organic frameworks (MOFs) assembled with diazatetracene (DAT)-based linkers are synthesized and characterized. Despite different chromophore orientations and spacings, photoinduced persistent radicals were generated in all the MOFs,...

Guest-responsive coherence time of radical qubits in a metal–organic framework

“…27 Although the details of the generation mechanism of the DAT radicals have not been fully understood, similar radical generation would also take place in the current DAT-MOF-4. The g value of the radical in DAT-MOF-4 was 2.0031, which is comparable to our previously reported DAT radical cation, 21,24 also supporting the formation of DAT radicals in DAT-MOF-4. In our previous report on another MOF (DAT-MOF-1) with a DAT derivative as a ligand, we performed Rabi oscillation experiments and identified it as radical species with S = 1/2 by comparing the oscillation frequency with photoexcited triplet species.…”

“…In our previous study, we observed that in three mixed-linker MOFs (DAT-MOF-1, 2, and 3) consisting of Zn ions, DPyDAT, and different co-ligands, photoirradiation induces the charge separation and the formation of DAT radical cations. 21,24 However, in the current DAT-MOF-4, the laser irradiation did not bring any increase of the ESR signal intensity. Meanwhile, even without light irradiation, continuous wave (CW)-ESR measurements of DAT-MOF-4 in the “dark” condition showed an ESR signal similar to the previously-observed ESR signal of DAT radicals (Fig.…”

“…Metal–organic frameworks (MOFs) provide an ideal platform for quantum sensing using molecular qubits. 9,16–24 Qubits can be integrated into MOFs during or after synthesis. Paramagnetic metal ions 16,17,19,23 and organic molecules 9,21,22,24 in doublet, triplet, and quintet states have been introduced into MOFs as qubits.…”

“…9,16–24 Qubits can be integrated into MOFs during or after synthesis. Paramagnetic metal ions 16,17,19,23 and organic molecules 9,21,22,24 in doublet, triplet, and quintet states have been introduced into MOFs as qubits. For the potential of chemical quantum sensing, the interactions between adsorbed guest molecules and qubits can be understood by estimating relaxation time and hyperfine interactions with electron spin resonance (ESR) measurements.…”

“…9,20 We have previously reported that MOFs consisting of pyridyl-modified 5,12-diazatetracene (DAT) ligands (DPyDAT) and Zn ions undergo charge separation from the photo-excited DAT chromophore, and that the resulting DAT radicals exhibit relatively long coherence times T 2 . 21,24 However, due to the instability of the MOF structure, the response of T 2 to various guest molecules could not be evaluated.…”