Polymorphism in [Cu(cyclam)(TCNQ)₂](TCNQ) Stacked Systems (cyclam = 1,4,8,11-Tetraazacyclotetradecane, TCNQ = 7,7,8,8-Tetracyanoquinodimethane)

Abstract

The compound [Cu(cyclam)(TCNQ)2](TCNQ) (cyclam = 1,4,8,11-tetraazacyclotetradecane, TCNQ = 7,7,8,8-tetracyanoquinodimethane) has been obtained in two different crystallographic forms, isomers 1 and 2. Crystal data for isomer 1: triclinic, P1̄, a = 7.855(6) Å, b = 10.267(2) Å, c = 14.424(3) Å, α = 95.42(2)°, β = 102.18(5)°, γ = 109.74(3)°, Z = 1. Crystal data for isomer 2: triclinic, P1̄, a = 8.165(1) Å, b = 9.918(3) Å, c = 13.278(3) Å, α = 83.91(2)°, β = 78.31(2)°, γ = 79.22(2)°, Z = 1. Both isomers show the same copper environment and oxidation states in the TCNQ molecules, and the only difference is observed in the stacking of the latter groups. The main common feature is the presence of parallel chains of copper macrocycle units linked by dimeric (TCNQ)2 2-, which coordinates to the metal. These chains are joined in isomer 1 by one neutral TCNQ molecule oriented parallel to the anionic TCNQ dimers and overlapping with two of them creating a bidimensional network. In contrast, the neutral TCNQ in isomer 2 is rotated about 70° relative to the anionic dimers and overlaps with four different chains, extending the interaction in a tridimensional way. The spectral and solid state conductivity data show electronic localization on the dimers (TCNQ)2 2- in both isomers with a weak semiconducting behavior. The magnetic behavior of both isomers can be interpreted as the sum of contributions from the metal and a thermally activated triplet state for the dimerized anions. The latter contribution is favored by the π overlap of the neutral TCNQ molecules, since the analogous derivative [Cu(cyclam)(TCNQ)2], only with anionic dimers, shows a strong antiferromagnetic coupling inside the dimers and no appreciable contribution to the bulk magnetic susceptibility is observed.

SYNTHESES, SPECTRA, AND MAGNETIC PROPERTIES OF Fe(II) COMPLEXES WITH 7,7′,8,8′- TETRACYANOQUINODIMETHANE

“…The transition at 11,765 cm À1 verifies the non-existence of neutral TCNQ, because in TCNQ 0 only a transition at around 25,400 cm À1 occurs. The ratio values of the two bands (e 23,697 =e 11,765 ¼ 0.5) further demonstrate that the solutions contain only TCNQ À species 12 .…”

Synthesis and characterization of cobalt(iii) cyanide complexes: cobalt participation in the decomposition of radical anion of TCNQ

“…This crude solid was dissolved in CH 2 Cl 2 and washed with water. After drying 30 over Na 2 SO 4 , the solvent was removed under vacuum and yellow oil was obtained. Yield: 3.52 g, 48.6%.…”

“…The two most often used methods to obtain chiral species are by 30 stereoselective synthesis using chiral species or by spontaneous resolution upon crystallization without any chiral auxiliary. [18][19][20][21] To prepare new chiral complexes, we focus our attention on TCNQ-based complexes incorporated organic auxiliary ligands H 2 salency(N,N'-Bis(salicylidene)-1,2-cyclohexanediamine) with 35 optical activity.…”

Radical Ion Salts Obtained from Substituted Ferrocene Cations and the Organic Acceptor TCNQ − Synthesis, Structure and Physical Properties

“…Thus, the reaction on the right-hand side of the equilibrium is the usual method of preparing the anion radical as its lithium salt. [24] We have used the reverse reaction in forming [Cu(cyclam) [25] The cationic charge in the ferrocene allows us to obtain derivatives of anionic TCNQ, either by iodide metathesis or by reduction from the neutral acceptor, but without any charge transfer that implies the iron atom. (3) is always obtained, either by reaction with LiTCNQ or with neutral TCNQ.…”

“…This is common for TCNQ derivatives that form the dimeric dianion [TCNQ] 2 2Ϫ . [25,48] The diamagnetism of compound 2 is surprising since the electronic delocalization is usually reflected in the magnetic susceptibility, either as a weak Pauli paramagnetism [64] or as the contribution of an S ϭ 1/2 spin 1D system with antiferromagnetic coupling. [23,65] The unexpected diamagnetism of 2 could suggest a higher localization of the TCNQ unpaired electrons, giving rise to a stronger antiferromagnetic coupling in the bulk.…”