Spectroscopic, Thermal, and Magnetic Properties of Metal/TCNQ Network Polymers with Extensive Supramolecular Interactions between Layers

Abstract

Reactions of [M(MeCN) n ][BF 4 ] 2 salts with Bu 4 N(TCNQ) in MeOH yield M(TCNQ) 2 (MeOH) x (M ) Mn, 1; Fe, 2; Co, 3; Ni, 4, x ) 2-4), and reactions of MnCl 2 , FeSO 4 ‚7H 2 O, CoSO 4 ‚7H 2 O and NiCl 2 ‚6H 2 O in H 2 O produce M(TCNQ) 2 (H 2 O) 2 (M ) Mn, 5; Fe, 6; Co, 7; Ni, 8). Infrared spectroscopy, powder X-ray diffraction and thermogravimetric analyses of 1-8 indicate that the products prepared in the same solvent constitute isostructural families of compounds.[Mn(TCNQ-TCNQ)(MeOH) 4 ] ∞ (9) crystallizes in the triclinic space group P1 h, a ) 7.2966( 8Compound 9 contains TCNQligands that have undergone an unusual σ-dimerization to [TCNQ-TCNQ] 2that acts as a tetradentate ligand to Mn(II) ions to give a 2-D staircase polymeric motif. The layers are connected by hydrogenbonds between axially coordinated MeOH from adjacent layers and MeOH located between the layers. Compound 10 exhibits a zigzag polymeric motif with equatorially bound TCNQderived ligands of two types; the edges of the layers consist of cis-µ-TCNQmolecules involved in π-stacking with TCNQunits from another layer and σ-[TCNQ-TCNQ] 2acting as a tetradentate bridging ligand. Axial MeOH ligands are hydrogen-bonded to dangling nitrile groups of cis-µ-TCNQligands in the next layer. Mn(TCNQ) 2 (H 2 O) 2 (11) crystallizes in the monoclinic space group I2/a, a ) 12.5843(7) Å, b ) 13.7147(7) Å, c ) 13.3525(70 Å, β ) 92.887(1)°, V ) 2301.58 Å 3 , Z ) 4. This material adopts a double-layer motif consisting of Mn(II) ions bonded to syn-µ 2 -TCNQequatorial ligands and axial H 2 O molecules. Compounds 1-11 exhibit Curie-Weiss behavior with weak antiferromagnetic coupling being observed at low temperatures. The Zn(II) analogue of 10, [Zn(TCNQ)(TCNQ-TCNQ) 0.5 (MeOH) 2 ] ∞ (12) was also prepared: space group C2/c, a ) 14.2252(1) Å, b ) 27.3290(4) Å, c ) 13.1177(2) Å, β ) 90.074(1)°, V ) 5099.64(11) Å 3 , Z ) 8. Powder X-ray diffraction was used to probe structures 1-11, and it was found that 9 converts to a new phase with heating or exposure to X-rays that is related to disruption of the σ-dimer (TCNQ-TCNQ) 2ligands and loss of MeOH. The new phase, whose powder pattern is identical with that of a phase prepared from MeCN, exhibits ferromagnetic behavior.

Tetracyanoethylene (TCNE): The Characteristic Geometries and Vibrational Absorptions of Its Numerous Structures

“…[97] [e] No characteristic ñ CN absorption owing to the presence of other nitriles, but all occur at 2233(sh), 2220(s), 2168(vs), and 1355(w). [98] [f] For R = CN, that is, C 3 (CN) 6 absorptions occur at 2290, 2250, 2220 cm À1 .…”

Water-controlled synthesis of low-dimensional molecular crystals and the fabrication of a new water and moisture indicator

“…3(a). The band at 2196 cm 1 occurs at lower energy than that of the [19,24]. The distinct difference in the TGA traces of the columns and lamellae possibly indicates that they are different phases.…”

Radical ligand-containing single-molecule magnets

“…The ligands being utilized for this purpose span a wide range, from the more established nitronyl nitroxide and benzosemiquinonoid ligands [51][52][53][54], to the more recently developed verdazyl, thiazyl, and carbene ligands that already show great promise in generating materials with interesting magnetic properties [55][56][57]. Although tetracyanoethylene, 7,7,8,8-tetracyanoquinodimethane, N,N -dicyanoquinonediimine, and perchlorotriphenylmethyl radicals have found enormous success in the rational design of molecule-based magnetic materials, they will not be covered in this section, owing to the lack of the corresponding molecular analogs [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75].…”