Iron Pentacarbonyl as a Precursor for Molecule-Based Magnets:  Formation of Fe[TCNE]₂(T_c= 100 K) and Fe[TCNQ]₂(T_c= 35 K) Magnets

Abstract

The reaction of tetracyanoethylene (TCNE) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) with Fe(CO)(5) leads to formation of magnetically ordered materials of Fe[TCNE](2) (T(c) = 100 K) and Fe[TCNQ](2) (T(c) = 35 K) composition, respectively. In contrast, the reaction with 1,2-dichloro-5,6-dicyanobenzoquinone (DDQ) leads to a paramagnetic material.

M[TCNQ]y-Based Magnets (M = Mn, Fe, Co, Ni; TCNQ = 7,7,8,8-tetracyano-p-quinodimethane)

“…Hence, the reaction of TCNQ and V(CO) 6 must not initially proceed by electron transfer, but by ligand substitution via nucelophilic attack of the TCNQ and concomitant CO loss, leading to intermediates that reduce the oxidation potential of the V. 21 By analogous reactions, M[TCNQ] y (M ) Fe, Ni, Co) have been synthesized from M a (CO) b and TCNQ (eq 1), although their mechanisms are unknown. Formation of Fe[TCNQ] 2 ‚zCH 2 Cl 2 from Fe(CO) 5 and TCNQ has been previously reported, 9 but the results are included herein for this comparative study.…”

“…8 In contrast, the reactions of Fe(CO) 5 with TCNE as well as TCNQ (TCNQ ) 7,7,8,8-tetracyano-p-quinodimethane, 1) form Fe [TCNE] 2 and Fe[TCNQ] 2 that magnetically order at 100 and 35 K, respectively. 9 The chemistry of TCNQ has been widely studied, 10 primarily due to its potential application in organic conductors. 10,11 M[TCNQ] y materials have previously been reported as methanol or water solvates, 10,12 as products of electrochemical synthesis, 11c and from Fe(CO) 5 9 and [M(NCMe) 6 [BF 4 ] -salts by Dunbar led to glassy magnetically ordered materials that incorporated the anion in the product, 13,14 and, in an attempt to identify a weaker binding anion, [SbF 6 ] -15 was selected to minimize the presence of the anion and enhance T c .…”

Laser Spectroscopy and Lifetime Measurements of the S1 State of Tetracyanoquinodimethane (TCNQ) in a Cold Gas‐Phase Free‐Jet

“…7,7,8,8‐Tetracyanoquinodimethane (TCNQ, Scheme ) is one of the most famed organic molecules, whose complex with tetrathiafulvalene (TTF) exhibits an exceptional electronic conductivity at low temperatures (∼10 4 S ⋅ cm −1 at 66 K); it is often called “organic metal” . Not only as the electron transport material, but TCNQ and its derivatives are extremely important as versatile doping agents for functional materials,,, components of organic magnets, Langmuir‐Blodgett films, field‐effect transistors,, organic crystals, and nonlinear optical materials . Understanding the electronic and photochemical properties of TCNQ is of fundamental importance for further development of this functional material .…”

Cross‐Linked Layered Structure of Magnetically Ordered [Fe(TCNE)2]⋅z CH2Cl2 Determined by Rietveld Refinement of Synchrotron Powder Diffraction Data

“…With the goal of identifying new organic‐based magnets, [Fe(TCNE) 2 ]⋅ z CH 2 Cl 2 ( T c ≈100 K)6a,b was prepared through the reaction of TCNE and FeI 2 6c or [Fe(CO) 5 ],6b and [Mn(TCNE) 2 ]⋅ z CH 2 Cl 2 ( T c ≈75 K)6d was formed from the reaction of TCNE and MnI 2 6c. Albeit important, the structures of [M(TCNE) 2 ]⋅ z CH 2 Cl 2 (M=V, Mn, Fe) have been elusive because of the unavailability of single crystals.…”