Magnetic Ordering in a Vanadium-Organic Coordination Polymer Using a Pyrrolo[2,3-\u3cem\u3ed\u3c/em\u3e:5,4-\u3cem\u3ed\u27\u3c/em\u3e]bis(thiazole)-Based Ligand

Here we present the synthesis and characterization of a hybrid vanadium-organic coordination polymer with robust magnetic order, a Curie temperature TC of ∼110 K, a coercive field of ∼5 Oe at 5 K, and a maximum mass magnetization of about half that of the benchmark ferrimagnetic vanadium(tetracyanoethylene)~2 (V·(TCNE)~2). This material was prepared using a new tetracyano-substituted quinoidal organic small molecule 7 based on a tricyclic heterocycle 4-hexyl-4H-pyrrolo[2,3-d:5,4-d′]bis(thiazole) (C6-PBTz). Single crystal X-ray diffraction of the 2,6-diiodo derivative of the parent C6-PBTz, showed a disordered hexyl chain and a nearly linear arrangement of the substituents in positions 2 and 6 of the tricyclic core. Density functional theory (DFT) calculations indicate that C6-PBTz-based ligand 7 is a strong acceptor with an electron affinity larger than that of TCNE and several other ligands previously used in molecular magnets. This effect is due in part to the electron-deficient thiazole rings and extended delocalization of the frontier molecular orbitals. The ligand detailed in this study, a representative example of fused heterocycle aromatic cores with extended π conjugation, introduces new opportunities for structure–magnetic-property correlation studies where the chemistry of the tricyclic heterocycles can modulate the electronic properties and the substituent at the central N-position can vary the spatial characteristics of the magnetic polymer

Characterisation of a dipolar chromophore with third-harmonic generation applications in the near-IR

E-2-Tricyanovinyl-3-n-hexyl-5-[4-{bis(4-n-butylphenyl)amino}-2-methoxystyryl]-thiophene, 1, has previously been used to demonstrate applications relying on frequency tripling of 1.55 μm light. Here we report the synthesis and chemical characterisation of 1, along with quantum-chemical calculations and additional experimental investigations of its third-order nonlinear properties that give more insight into its frequency tripling properties. Although 1 can be processed into amorphous films, crystals can also be grown by slow evaporation of solutions; the crystal structure determined by X-ray diffraction shows evidence of significant contributions from zwitterionic resonance forms to the ground-state structure, and reveals centrosymmetric packing exhibiting π–π and C–H···N≡C interactions. Both solutions and films of 1 exhibit near-infrared two-photon absorption into the low-lying one-photon-allowed state with a peak two-photon cross-section of cɑ. 290 GM (measured using the white-light continuum method with a pump wavelength of 1800 nm) at a transition energy equivalent to degenerate two-photon absorption at cɑ. 1360 nm; two related chromophores are also found to show comparable near-IR two-photon cross-sections. Closed-aperture Z-scan measurements and quantum-chemical calculations indicate that the nonlinear refractive index and third-harmonic generation properties of 1 are strongly dependent on frequency in the telecommunications range, due the aforementioned two-photon resonance

Crystal structure of N,N,N-triethylhydroxylammonium chloride

In the title molecular salt, C6H16NO+·Cl−, two of the C—C—N—O groups in the cation adopt a gauche conformation [torsion angles = 62.86 (11) and −54.95 (13)°] and one an anti conformation [−177.82 (10)°. The cation and anion are linked by an O—H...Cl hydrogen bond. The extended structure displays C—H...Cl and C—H...O hydrogen bonds, resulting in layers lying parallel to the (100) plane: further C—H...Cl contacts connect the sheets into a three-dimensional network

Characterisation Of A Dipolar Chromophore With Third-Harmonic Generation Applications In The Near-Ir

We apply a general theoretical model to study the dissociative recombination of the polyatomic ion NH +4. The high symmetry of the molecule, represented by the tetrahedral group, leads to complex vibronic couplings responsible for dissociative recombination. By applying multi-channel quantum defect theory and using symmetry considerations, we treat the doubly and triply degenerate modes and electronic states of NH +4 to calculate a theoretical cross section. The cross section agrees well with existing experimental data. © 2012 IOP Publishing Ltd

Tunable third-harmonic generation from polaritons in the ultrastrong coupling regime

Strong inter-particle interactions between polaritons have traditionally stemmed from their exciton component. In this work, we impart a strong photonic nonlinearity to a polaritonic mode by embedding a nonlinear polymethine dye within a high-Q all-metal microcavity. We demonstrate nonlinear microcavities operating in the ultrastrong coupling regime with a normalized coupling ratio of 62\%, the highest reported to date. When pumping the lower polariton branch, we observe tunable third-harmonic generation spanning the entire visible spectrum, with internal conversion enhancements more than three orders of magnitude larger than in bare films. Transfer matrix calculations indicate that the observed enhancements are consistent with the enhanced pump electric field.Comment: 7 pages, 5 figure

Parallel and Perpendicular Packing in Mixed-Stack Cocrystals of Trimeric Perfluoro-<i>ortho</i>-phenylene Mercury and Benzo[1,2‑<i>b</i>:6,5‑<i>b</i>′]­dithiophene-4,5-dione Derivatives

Seven cocrystals derived from 2,7-substituted benzo­[1,2-<i>b</i>:6,5-<i>b</i>′]­dithiophene-4,5-diones (BDDO) and trimeric perfluoro-<i>o</i>-phenylene mercury (TPPM) exhibit two prominent packing motifs: parallel mixed stacks and T-shaped columnar structures. The varied packing patterns reveal an interplay of noncovalent intermolecular interactions that depend on the nature of the BDDO 2,7-substituents and on the crystallization conditions. Quantum-chemical analyses show little charge-transfer character in the mixed-stack structures, suggesting limited electronic interaction among the mixed TPPM and BDDO constituents. The variations in molecular packing with rather minimal change in chemical structure expose the ability to fine-tune the structure of these molecular cocrystals

Easily Reducible Materials from the Reactions of Diselenopheno[3,2‑<i>b</i>:2′,3′-d]pyrrole and Dithieno[3,2‑<i>b</i>:2′,3′‑<i>d</i>]pyrrole with Tetracyanoethylene

A new core, 4<i>H</i>-diselenopheno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole (DSP), was reacted with tetracyanoethylene, and three products, mono-tricyanovinyl, bis-tricyanovinyl, and quinoidal, were isolated and compared with the respective 4<i>H</i>-dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole (DTP) derivatives using cyclic voltammetry, UV–vis absorption, and differential scanning calorimetry analyses. Organic field-effect transistors were fabricated using solution-processed films, and only one derivative, bis-tricyanovinyl-DSP, exhibited transistor behavior with μ_e reaching 8.7 × 10^–4 cm²/V·s. This enhancement of the electron-transporting properties in comparison with DTP derivative is attributed to stronger LUMO–LUMO interaction due to a larger size of selenium atom, which in the case of the bis-tricyanovinyl derivative, has wave function density on the chalcogen

Unusual Electronic Structure of the Donor–Acceptor Cocrystal Formed by Dithieno[3,2‑<i>a</i>:2′,3′‑<i>c</i>]phenazine and 7,7,8,8-Tetracyanoquinodimethane

Mixed cocrystals derived from electron-rich donor (D) and electron-deficient acceptor (A) molecules showcase electronic, optical, and magnetic properties of interest for a wide range of applications. We explore the structural and electronic properties of a cocrystal synthesized from dithieno­[3,2-<i>a</i>:2′,3′-<i>c</i>]­phenazine (DTPhz) and 7,7,8,8-tetracyanoquinodimethane (TCNQ), which has a mixed-stack packing arrangement of the (π-electronic) face-to-face stacks in a 2:1 D:A stoichiometry. Density functional theory investigations reveal that the primary electronic characteristics of the cocrystal are not determined by electronic interactions along the face-to-face stacks, but rather they are characterized by stronger electronic interactions orthogonal to these stacks that follow the edge-to-edge donor–donor or acceptor–acceptor contacts. These distinctive electronic characteristics portend semiconducting properties that are unusual for semiconducting mixed cocrystals and suggest further potential to design organic semiconductors with orthogonal transport characteristics for different charge carriers

Near-Infrared Asymmetrical Squaraine Sensitizers for Highly Efficient Dye Sensitized Solar Cells: The Effect of π‑Bridges and Anchoring Groups on Solar Cell Performance

Conventional squaraine dyes exhibit an intense absorption band in the red region of the solar spectrum and with appropriate design can also have high energy absorption as well, making them interesting building blocks toward achieving panchromatic dyes for dye sensitized solar cell (DSSC) applications. In this report, eight squaraine dyes with thiophene, 4-hexyl-4<i>H</i>-dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole, dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­thiophene, and 4,4-bis­(2-ethylhexyl)-4<i>H</i>-silolo­[3,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene (DTS) π-bridges with cyanoacetic acid (CA) and cyanophosphonic acid (PA) acceptor/anchoring groups are synthesized to extend the squaraine absorption into the 450–550 nm region and to provide different spatial arrangements of solubilizing groups. Squaraines with CA anchoring groups have higher power conversion efficiencies compared to their PA analogs, with the highest being 8.9% for the DTS-based dye, which is among the highest reported in the literature for squaraine dyes. This is due to high short circuit currents (<i>J</i>_SC) and increased open circuit voltages (<i>V</i>_OC). Dyes with PA anchoring groups exhibited lower <i>J</i>_SC resulting from decreased charge injection efficiency, as determined by femtosecond transient absorption spectroscopy. This study suggests that out-of-plane bulky substituents may increase DSSC performance not only by increasing <i>J</i>_SC through decreased aggregation but also by increasing <i>V</i>_OC through decreased TiO₂/electrolyte recombination