Dana J. Eisler

Crystal structures, EPR and magnetic properties of 2-ClC6H4CNSSN˙ and 2,5-Cl2C6H3CNSSN˙

The β-sheet structure associated with chlorinated aromatics (d(Cl···Cl)≈ 4.0 Å) has been implemented to drive formation of π-stacked structures of dithiadiazolyl radicals. Both title compounds exhibit an increase in paramagnetism above 150 K but solid-state EPR studies indicate that the origin of the paramagnetism in these two systems is different.

Molecular tailoring of spin-transition materials: preparation, crystal structure and magnetism of trifluoromethyl-pyridyl-1,3,2-dithiazolyl

The α-phase of pyridyl-1,3,2-dithiazolyl, pyDTA, has previously been shown to exhibit a distorted π-stacked structure which is diamagnetic at low temperature. Unlike other π-stacked dithiazolyl radicals it does not undergo a first order phase transition to a regular π-stacked paramagnetic phase even upon warming to its melting point. Here we show that incorporation of a trifluoromethyl group destabilises the diamagnetic π*–π* dimer and the title compound (1) exhibits a spin-transition (without hysteresis) at 50 K.

Weakening of the π*–π* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl2C6H3CNSSN

A series of dichlorophenyl dithiadiazolyls (DCP-DTDA) have been prepared and structurally characterized by X-ray diffraction (1 = 2,3-DCP-DTDA; 2 = 2,4-DCP-DTDA; 3 = 2,5-DCP-DTDA, 4 = 3,4-DCP-DTDA and 5 = 3,5-DCP-DTDA). All the radicals adopt cis-cofacial π*–π* dimers with intra-dimer S⋯S contacts in the range 3.119(8)–3.300(5) A. The propensity for chloro-aromatics to adopt a β-sheet structure assists formation of lamellar structures in 1–5 with intra-stack Cl⋯Cl contacts in the range 3.44(1)–3.82(1) A. Perpendicular to the stacking direction, the packing is dominated by formation of intermolecular S⋯Cl contacts. Variable-temperature magnetic susceptibility measurements on 1–5 in the range 5–300 K reveal the onset of paramagnetism around ca. 200 K. Solid-state EPR studies reveal that this paramagnetism is associated with thermal population of a triplet excited state. A good fit to the Bleaney–Bowers model determined the exchange interactions (2J) between the radicals in the dimers to be in the range −904 to −1529 cm−1. Computational studies of the dimerisation process indicate that at intra-dimer S⋯S distances in excess of 3.2 A the closed-shell singlet becomes destabilized with respect to both the open-shell singlet and triplet state configurations.

Formation of N-bridgehead 1,2,5-thiadiazolium and selenadiazolium rings through an intramolecular cyclisation reaction

Treatment of N-lithiopyridylketimide derivatives Li[R(C=N)py] (R=Ph, py) with ECl(2) (E=S, Se) affords the fused thiadiazolium and selenadiazolium salts [RC(6)H(4)N(2)E]Cl [1]Cl and [2]Cl containing a bridgehead N atom through intramolecular coordination.

Synthesis and structure of the li-13 cage [{[o - p(mu-(nbu)-bu-t)](2)li-2}(3)(licl)(6)li(cl/(obu)-bu-n)(0.5)(thf)(7)], containing a [o - p(mu-(nbu)-bu-t)](2)(2-) dianion

The hydrolysis of [ClP(mu-NtBu)]2 with H2O-Et3N in thf, followed by in situ lithiation with nBuLi gives the Li13 cage [[[O-P(mu-NtBu)]2Li2]3(LiCl)6Li(Cl/OnBu)0.5(thf)7], containing a [O-P(mu-NtBu)]2(2-) dianion that is isoelectronic with ligands of the type [(RN)P(mu-NR)]2(2-).

Syntheses of, and structural studies on, benzo-fused 1,2,4-thiadiazines

The syntheses of nine benzo-fused-1,2,4-thiadizines are reported. The use of microwave synthesis has been shown to afford high yields and short reaction times in several key reaction steps. The molecular geometries of these heterocycles are discussed and their solid state packing motifs reveal a strong tendency for the N–H group to form hydrogen bonded chains.

Joining the crown family; the tetrameric, O-bridged macrocycle [{P(μ-NtBu)}2(μ-O)]4

The in situ reaction of the dianion [O_P(micro-N(t)Bu)]2(2-) with the dimer [ClP(micro-N(t)Bu)]2 gives the O_bridged macrocycle [{P(micro-N(t)Bu)}2(micro-O)]4 (1), being the largest crown-like phosph(III)azane of its type to be reported and having a structure that is directly related to the ubiquitous 12-crown-4.

Synthesis and structural studies on thioimides, R2CNSR and sulfur diimides, R2CNSNCR2

Reaction of Ph(2)C=O and py(2)C=O with Li[N(SiMe(3))(2)] and ArSCl (Ar = 2-O(2)NC(6)H(4), 2,4-(O(2)N)(2)C(6)H(3)) yielded Ph(2)C=NSAr (1a and 1b respectively) and py(2)C=NSAr (2a and 2b respectively). Reaction of fluorenone, C(12)H(8)C=O with Li[N(SiMe(3))(2)] and ArSCl under similar conditions afforded C(12)H(8)CNSAr (3a and 3b respectively). Whilst reaction of fluorenone with Li[N(SiMe(3))(2)] and SCl(2) in a 2 : 2 : 1 ratio afforded the sulfur-diimide, C(12)H(8)CNSNCC(12)H(8) (4), reaction of py(2)C=O with Li[N(SiMe(3))(2)] and SCl(2) under similar conditions afforded the thiazyl heterocycle [py(2)CNS]Cl (5) via intramolecular coordination. The structures of 1a, 1b, 2a, 2b, 3a, 3b and 4 are determined by X-ray diffraction. In the case of 4, bond lengths and DFT studies reveal greater π-delocalisation than in 1-3.

[{(18-crown-6)K}GaCl4]∞, a diamondoid structure templated by tetrahedral GaCl4− ions

The simple complex formed between 18-crown-6 and potassium tetrachlorogallate, [{(18-crown-6)K}GaCl4]∞ (1), exhibits a diamondoid lattice arrangement in the solid state that is directed by the tetrahedral GaCl4− anions.