Verdazyls as Possible Building Blocks for Multifunctional Molecular Materials: A Case Study on 1,5-Diphenyl-3-(p-iodophenyl)-verdazyl Focusing on Magnetism, Electron Transfer and the Applicability of the Sonogashira-Hagihara Reaction

Abstract

This work explores the use of Kuhn verdazyl radicals as building blocks in multifunctional molecular materials in an exemplary study, focusing on the magnetic and the electron transfer (ET) characteristics, but also addressing the question whether chemical modification by cross-coupling is possible. The ET in solution is studied spectroscopically, whereas solid state measurements afford information about the magnetic susceptibility or the conductivity of the given samples. The observed results are rationalized based on the chemical structures of the molecules, which have been obtained by X-ray crystallography. The crystallographically observed molecular structures as well as the interpretation based on the spectroscopic and physical measurements are backed up by DFT calculations. The measurements indicate that only weak, antiferromagnetic (AF) coupling is observed in Kuhn verdazyls owed to the low tendency to form face-to-face stacks, but also that steric reasons alone are not sufficient to explain this behavior. Furthermore, it is also demonstrated that ET reactions proceed rapidly in verdazyl/verdazylium redox couples and that Kuhn verdazyls are suited as donor molecules in ET reactions.

Bipolar Verdazyl Radicals for Symmetrical Batteries: Properties and Stability in All States of Charge

“…Encouraged by these observations, the preparative‐scale chemical synthesis of 1 + and 1 − was performed. The cation 1 + was obtained as purple crystals in 94 % isolated yield by treatment of 1 with [NO][BF 4 ] in DCM, and characterized by spectroscopic methods and X‐ray crystallography [25] . Anion 1 − was prepared by reduction with Na/Hg in THF, and was isolated in 47 % yield as the tetrabutylammonium salt by exchange of the Na + cation with Bu 4 NBr.…”

“…Synthesis of 2,4,6‐triphenyl‐1,2,3,4‐tetrahydro‐1,2,4,5‐tetrazine (1H) . In accordance to a literature procedure by Jobelius et al ., [18b] with slight modification, ascorbic acid (0.084 g, 0.48 mmol, 1.5 eq.) was added to a Schlenk flask containing a solution of 1 (0.100 g, 0.32 mmol) in 5 mL THF and stirred overnight under inert atmosphere.…”

The syntheses, structures and spectroelectrochemical properties of 6-oxo-verdazyl derivatives bearing surface anchoring groups

“…13 These potential applications have prompted renewed interest in the synthetic chemistry associated with verdazyl-based structures, 14,15 including demonstrations of Sonogashira cross-coupling reactions that have been used to extend the conjugation of aryl groups at either the 1-or 3-positions. 16,17 More generally, radical molecular species have been identified as exceptionally promising compounds for use in the development of the field of molecular electronics. [18][19][20][21][22][23] The incorporation of a molecular system featuring an unpaired electron within an electrode | molecule | electrode junction leads to a host of fascinating electronic properties, 24 including enhanced rectification, 25 spin-gating, 26 Kondo effects, 27 magnetoresistive effects 28 and quantum interference, 29 whilst the redox-activity of such systems allows for an exciting range of electrochemically gated applications.…”

1,2,5-Thiadiazole 1,1-dioxides and Their Radical Anions: Structure, Properties, Reactivity, and Potential Use in the Construction of Functional Molecular Materials

“…The oxo- and dioxothiadiazoles can be easily reduced to stable radical anions [ 21 ] and are therefore of potential use to the molecular magnetism community. However, this group of compounds seems to be completely omitted as potential building blocks for the construction of molecule-based magnetic materials [ 22 , 23 ] compared to other organic radicals (nitronyl nitroxides [ 24 , 25 , 26 , 27 ], verdazyl [ 28 , 29 , 30 ], semiquinones [ 31 , 32 ], or TCNE and TCNQ derivatives [ 33 , 34 ]) which have been used extensively to obtain all-organic magnets [ 35 ], Single Molecule Magnets [ 36 , 37 ], or Single Chain Magnets (SCMs) [ 24 , 38 , 39 , 40 , 41 ], among many other functional magnetic materials. This review focuses on 1,2,5-thiadiazole 1,1-dioxides ( Figure 1 a) and their radical anions [ 42 ], which constitute perhaps the prime example of the dioxothiadiazole family, and summarizes the current state-of-the-art in the field of 1,2,5-thiadiazole 1,1-dioxides with the aim of shedding light on the extraordinary possibilities and applications of this heterocyclic moieties with respect to the design and preparation of switchable/functional molecular materials.…”