2D Arrays of Organic Qubit Candidates Embedded into a Pillared-Paddlewheel Metal–Organic Framework

Abstract

The creation of ordered arrays of qubits that can be interfaced from the macroscopic world is an essential challenge for the development of quantum information science (QIS) currently being explored by chemists and physicists. Recently, porous metal–organic frameworks (MOFs) have arisen as a promising solution to this challenge as they allow for atomic-level spatial control of the molecular subunits that comprise their structures. To date, no organic qubit candidates have been installed in MOFs despite their structural variability and promise for creating systems with adjustable properties. With this in mind, we report the development of a pillared-paddlewheel-type MOF structure that contains 4,7-bis­(2-(4-pyridyl)-ethynyl) isoindoline N-oxide and 1,4-bis­(2-(4-pyridyl)-ethynyl)-benzene pillars that connect 2D sheets of 9,10-dicarboxytriptycene struts and Zn2(CO2)4 secondary binding units. The design allows for the formation of ordered arrays of reorienting isoindoline nitroxide spin centers with variable concentrations through the use of mixed crystals containing the secondary 1,4-phenylene pillar. While solvent removal causes decomposition of the MOF, magnetometry measurements of the MOF containing only N-oxide pillars demonstrated magnetic interactions with changes in magnetic moment as a function of temperature between 150 and 5 K. Variable-temperature electron paramagnetic resonance (EPR) experiments show that the nitroxides couple to one another at distances as long as 2 nm, but act independently at distances of 10 nm or more. We also use a specially designed resonance microwave cavity to measure the face-dependent EPR spectra of the crystal, demonstrating that it has anisotropic interactions with impingent electromagnetic radiation.

Impact of Polymer Rigidity on Thermoresponsive Luminescence and Electron Spin Resonance of Polyester-Tethered Single Radicals

“…The line broadening could be mainly attributed to the slower rotation of the electron spin and longer rotational correlation times of the radical polymers at 100 K compared to them at RT. [23,34] The trend of Hpp of four RPEs is Hpp(RPE6) < Hpp(RPE4) < Hpp(RPE2) < Hpp(RPE1) (Table 2), consistent with greater mobility of radical molecule in more flexible polyesters. Finally, we compared ESR properties of RPE2 and RPE3 with different chain lengths of the PCL (Figure 3b, Figure S23, Table 2).…”

“…For example, to reduce the influence of intermolecular electron-electron interactions on spin relaxation, Pei and co-workers [20] reported Rabi cycles with a remarkable coherence time beyond one microsecond under ambient condition by dispersing triphenylmethyl radicals in a nonspin lattice of the radical precursors with a molar ratio of 1:1000. Overall, current methods of dispersing radicals in a nonspin lattice of the radical precursors, polymeric matrices or molecular organic frameworks [21][22][23] still face challenges of tuning the inter-radical aggregation in a controllable and well-defined way.…”

Enhancing Capacity and Stability of Anionic MOFs as Electrode Material by Cation Exchange

“…MOFs are porous materials that belong to the continuously growing class of polymeric coordination compounds, whose potential applications range from the well-known gas storage and separation (Han et al, 2009;Murray et al, 2009;Suh et al, 2012), catalysis (Lee et al, 2009;Ma et al, 2009;Dhakshinamoorthy and Garcia, 2012), magnetism (Kurmoo, 2009;Dechambenoit and Long, 2011;Weng et al, 2011;Campo et al, 2016), drug delivery (Horcajada et al, 2008;Horcajada et al, 2010;Sun et al, 2013) and sensing (Xiao et al, 2010;Kreno et al, 2012) to the lesser known utilizations as spin qubits (Yamabayashi et al, 2018;Jellen et al, 2020;Yu et al, 2020). The general motif of their structures typically involves a polytopic organic ligand that is coordinatively linked to transition metal centers or clusters via donor atoms such as oxygen or nitrogen (Cook et al, 2013;Ghasempour et al, 2021).…”

Radicals Persistent above 300 ℃: from Framework Design to Solar Vapor Generation

“…Besides various reactions on the ethene and S functions, ring contraction can occur to form the 6earomatic thiophenes; 26,27 the alternative, 1,3-dithiole radical 28,29 product (Scheme 1) has not been generated from dithiin precursors, but would enrich radical-containing MOF solids. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] The tailorable spatial order of solid state frameworks offers unique opportunity to trap reactive species and to channel reaction pathways. [46][47][48][49][50][51][52][53][54] Notably, Matsuda and Ma reported spatially isolated carbene sites at the midpoints of the long linkers in a rigid open MOF scaffold, 55 and their higher decomposing temperature (170 K), relative to the control carbene species (80 K; in a frozen matrix of 2methyltetrahydrofuran).…”