Dithiazolo[5,4‐b:4′,5′‐d]phosphole: A Highly Luminescent Electron‐Accepting Building Block

A family of highly emissive dithiazolo[5,4‐b:4′,5′‐d]phospholes has been designed and synthesized. The structures of two trivalent P species, as well as their corresponding P oxides, have been confirmed by X‐ray crystallography. The parent dithiazolo[5,4‐b:4′,5′‐d]phosphole oxide exhibits strong blue photoluminescence at λ_em=442 nm, with an excellent quantum yield efficiency of ?_PL=0.81. The photophysical properties of these compounds can be easily tuned by extension of the conjugation and modification of the phosphorus center. Compared with the established dithieno[3,2‐b:2′,3′‐d]phosphole system, the incorporation of electronegative nitrogen atoms leads to significantly lowered frontier orbital energy levels, as validated by both electrochemistry and theoretical calculations, thus suggesting that the dithiazolo[5,4‐b:4′,5′‐d]phospholes are valuable, air‐stable, n‐type conjugated materials. These new building blocks have been further applied to the construction of an extended oligomer with fluorene. Extension of the dithiazolophosphole core with triazole units through click reactions also provides a suitable N,N‐chelating moiety for metal binding and a representative molecular species was successfully used as a selective colorimetric and fluorescent sensor for Cu^II ions.     

Halogen bonding in 1,2‐dibromo‐4,5‐dimethoxybenzene and 1,2‐diiodo‐4,5‐dimethoxybenzene

An interesting case of `halogen‐bonding‐promoted' crystal structure architecture is presented. The two title compounds, C₈H₈Br₂O₂ and C₈H₈I₂O₂, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen‐bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a π‐bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C—Br...Br—C links and with no C—Br...O/N interactions present. In the diiodo structure, instead, the C—I...O synthon prevails, defining linear chains, in turn interlinked by C—I...I—C interactions.     

α,α′‐Diarylacenaphtho[1,2‐c]phosphole P‐Oxides: Divergent Synthesis and Application to Cathode Buffer Layers in Organic Photovoltaics

A divergent method for the synthesis of α,α′‐diarylacenaphtho[1,2‐c]phosphole P‐oxides has been established; α,α′‐dibromoacenaphtho[c]phosphole P‐oxide, which was prepared through a Ti^II‐mediated cyclization of 1,8‐bis(trimethylsilylethynyl)naphthalene, underwent a Stille coupling with three different kinds of aryltributylstannanes to afford the α,α′‐diarylacenaphtho[c]phosphole P‐oxides in moderate to good yields. X‐ray crystallographic analyses and UV/Vis absorption/fluorescence measurements have revealed that the degree of π‐conjugation, the packing motif, the electron‐accepting ability, and the thermal stability of the acenaphtho[c]phosphole π‐systems are finely tunable with the α‐aryl substituents. All the P?O and P?S derivatives exhibited high stability in their electrochemically reduced state. To use this class of arene‐fused phosphole π‐systems as n‐type semiconducting materials, we evaluated device performances of the bulk heterojunction organic photovoltaics (OPV) that consist of poly(3‐hexylthiophene), an indene‐C₇₀ bisadduct, and a cathode buffer layer. The insertion of the diarylacenaphtho[c]phosphole P‐oxides as the buffer layer was found to improve the power conversion efficiency of the polymer‐based OPV devices.     

3,4‐Dithiaphosphole and 3,3′,4,4′‐Tetrathia‐1,1′‐Biphosphole π‐Conjugated Systems: S Makes the Impact

Conjugated systems based on phospholes and 1,1′‐biphospholes bearing 3,4‐ethylenedithia bridges have been prepared using the Fagan–Nugent route. The mechanism of this organometallic route leading to intermediate zirconacyclopentadienes has been investigated by using theoretical calculations. This study revealed that the oxidative coupling leading to zirconacyclopentadienes is favored over oxidative addition within the S? C≡C bond both thermodynamically and kinetically. The impact of the presence of the S atoms on the optical and electrochemical behavior of the phospholes and 1,1′‐biphospholes has been systematically evaluated both experimentally and theoretically. A comparison with their “all‐carbon” analogues is provided. Of particular interest, this comparative study revealed that the introduction of S atoms has an impact on the electronic properties of phosphole‐based conjugated systems. A decrease of the HOMO–LUMO separation and a stabilization of the LUMO level were observed. These general trends are also observed with 1,1′‐biphospholes exhibiting σ–π conjugation. The P atom of the 3,4‐ethylenedithiaphospholes can be selectively oxidized by S₈ or O₂. These P modifications result in a lowering of the HOMO–LUMO separation as well as an increase of the reduction and oxidation potentials. The S atoms of the 3,4‐ethylenedithia bridge of the 2,5‐phosphole have been oxidized using m‐chloroperoxybenzoic acid. The resulting 3,4‐ethylenesulfoxide oxophosphole was characterized by an X‐ray diffraction study. Experimental and theoretical studies show that this novel chemical manipulation results in an increase of the HOMO–LUMO separation and an important decrease of the LUMO level. The electropolymerization of 2‐thienyl‐capped 3,4‐ethylenedithiathioxophosphole and 1,1′‐biphosphole is reported. The impact of the S substituents on the polymer properties is discussed.     

Synthesis and Structure–Property Relationships of 2,2′‐Bis(benzo[b]phosphole) and 2,2′‐Benzo[b]phosphole–Benzo[b]heterole Hybrid π Systems

The first comprehensive study of the synthesis and structure–property relationships of 2,2′‐bis(benzo[b]phosphole)s and 2,2′‐benzo[b]phosphole–benzo[b]heterole hybrid π systems is reported. 2‐Bromobenzo[b]phosphole P‐oxide underwent copper‐assisted homocoupling (Ullmann coupling) and palladium‐catalyzed cross‐coupling (Stille coupling) to give new classes of benzo[b]phosphole derivatives. The benzo[b]phosphole–benzo[b]thiophene and ‐indole derivatives were further converted to P,X‐bridged terphenylenes (X=S, N) by a palladium‐catalyzed oxidative cycloaddition reaction with 4‐octyne through the C_β? H activation. X‐ray analyses of three compounds showed that the benzo[b]phosphole‐benzo[b]heterole derivatives have coplanar π planes as a result of the effective conjugation through inter‐ring C? C bonds. The π–π* transition energies and redox potentials of the cis and trans isomers of bis(benzo[b]phosphole) P‐oxide are very close to each other, suggesting that their optical and electrochemical properties are little affected by the relative stereochemistry at the two phosphorus atoms. The optical properties of the benzo[b]phosphole–benzo[b]heterole hybrids are highly dependent on the benzo[b]heterole subunits. Steady‐state UV/Vis absorption/fluorescence spectroscopy, fluorescence lifetime measurements, and theoretical calculations of the non‐fused and acetylene‐fused benzo[b]phosphole–benzo[b]heterole π systems revealed that their emissive excited states consist of two different conformers in rapid equilibrium.     

New P‐ligands: The aromaticity and reactivity of 2,4,6‐trialkylphenylphospholes

A further member of 2,4,6‐trialkyl‐phenyl‐phos‐pholes, the ditertbutylmethylphenyl derivative ( 1c ) was characterized by Bird index and by the sum of angles at the phosphorus atom to describe the flattening of the P‐pyramid. Both numbers suggested a slight aromaticity. The reaction of arylphospholes with phosphorus tribromide was extended to phosphole 1c leading this occasion, after further steps, to the mixture of 3‐ and 2‐substituted products ( 3c‐1 and 3c‐2 , respectively). A triisopropylphenyl‐2H‐phosphole ( 4 ) formed by sigmatropic rearrangement was utilized in the preparation of new 1‐phosphanorbornene derivatives, such as sulfide 6 and hemi‐oxides 8‐1 and 8‐2 . Further oxidation of the latter species ( 8‐1 and 8‐2 ) led to the decomposition of the dimeric structure ( 11 ). 4 could also be trapped by benzaldehyde to afford the oxaphosphanorbornene ( 10 ) as one diastereomer. Finally, the reversible formation of 2H‐phosphole 4 from 1H‐phosphole 1a at 150°C was proved. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:104–222, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20077     

catena‐Poly­[[aqua(2,2′‐bi­pyridine‐κ2N,N′)­manganese(II)]‐μ‐terephthalato‐κ3O,O′:O′′]

The title complex, [Mn(C₈H₄O₄)(C₁₀H₈N₂)(H₂O)]_n, takes the form of a zigzag chain, with the terephthalate dianion (tp) acting as a tridentate ligand. The Mn^II center is surrounded by two tp ligands, one water mol­ecule and one 2,2′‐bi­pyridine (bipy) ligand and exhibits a severely distorted octahedral coordination environment, with cis angles ranging from 57.31 (8) to 123.97 (11)°. The complete solid‐state structure can be described as a three‐dimensional supramolecular framework stabilized by hydrogen‐bonding interactions involving the coordinated water mol­ecule and the carboxy O atoms of the tp ligands, and by π–π stacking interactions involving the bipy rings and the benzene ring of the tp ligand.     

Band‐gap engineering of polythiophenes via dithienophosphole doping

A series of polythiophenes doped with dithieno[3,2‐b:2′,3′‐d]phosphole units at varying levels (0–17%) were synthesized and characterized. Polymer work up provided two series of polymers from chloroform (C) and hexanes (H) for each doping level, respectively. Systematic structure–property studies revealed that the C‐series polymers generally had higher molecular weights than the H‐series, but also slightly higher relative dithienophosphole concentrations, both having a significant impact on the photophysical and electrochemical properties of the polymers. Furthermore, the presence of the dithienophosphole units also stabilizes the LUMO levels, whereas the HOMO levels remain dominated by the thiophene units, resulting in desirable electronics for an interaction with acceptor materials, such as 1‐(3‐methoxycarbonyl)propyl‐1‐phenyl[6,6]C₆₁. Importantly, increasing amount of dithienophosphole doping results in increased conductivities for the polymers in their oxidized state, while concurrently significantly stabilizing the neutral polythiophenes toward oxidation under environmental conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Anion‐Binding Catalysis by Electron‐Deficient Pyridinium Cations

A new activation principle in organocatalysis is presented: halide binding through Coulombic interactions. This mode of catalysis was realized by using 3,5‐di(carbomethoxy)pyridinium ions that carry an additional electron‐withdrawing substituent on the nitrogen atom, for example, pentafluorobenzyl or cyanomethyl. For the N‐pentafluorobenzyl derivative, Coulombic interaction with the pyridinium moiety is complemented in the solid state by anion–π interactions with the perfluorophenyl ring. Bromide and chloride are bound by these cations in a 1:1 stoichiometry. Catalysis of the C? C coupling between 1‐chloroisochroman (and related electrophiles) with silyl ketene acetals occurs at ?78 °C and at low catalyst loading (2 mol %).     

Supramolecular Assemblies of (±-2,2''''-Dihydroxy-1,1''''-binaphthyl with 2,2''''-Bipyridine and Naphthodiazine

Introduction Optically active 1,1'-bi-2-naphthol (BINOL) and its derivatives have been widely used as chiral ligands of catalysts for asymmetric reactions and effective host compounds for the isolation or optical resolution of a wide range of organic guest molecules through the for-mation of crystalline inclusion complexes.1,2 The wide-ranging and important applications of these com-pounds in organic synthesis have stimulated great inter-est in developing efficient methods for their prepara-…     

How the oxazole fragment influences the conformation of the tetraoxazocane ring in a cyclohexanespiro‐3′‐(1,2,4,5,7‐tetraoxazocane): single‐crystal X‐ray and theoretical study

Single crystals of (2S,5R)‐2‐isopropyl‐5‐methyl‐7‐(5‐methylisoxazol‐3‐yl)cyclohexanespiro‐3′‐(1,2,4,5,7‐tetraoxazocane), C₁₆H₂₆N₂O₅, have been studied via X‐ray diffraction. The tetraoxazocane ring adopts a boat–chair conformation in the crystalline state, which is due to intramolecular interactions. Conformational analysis of the tetraoxazocane fragment performed at the B3LYP/6‐31G(d,2p) level of theory showed that there are three minima on the potential energy surface, one of which corresponds to the conformation realized in the solid state, but not to a global minimum. Analysis of the geometry and the topological parameters of the electron density at the (3,?1) bond critical points (BCPs), and the charge transfer in the tetraoxazocane ring indicated that there are stereoelectronic effects in the O—C—O and N—C—O fragments. There is a two‐cross hyperconjugation in the N—C—O fragment between the lone electron pair of the N atom (lpN) and the antibonding orbital of a C—O bond (σ*_C—O) and vice versa between lpO and σ*_C—N. The oxazole substituent has a considerable effect on the geometry and the topological parameters of the electron density at the (3,?1) BCPs of the tetraoxazocane ring. The crystal structure is stabilized via intermolecular C—H…N and C—H…O hydrogen bonds, which is unambiguously confirmed with PIXEL calculations, a quantum theory of atoms in molecules (QTAIM) topological analysis of the electron density at the (3,?1) BCPs and a Hirshfeld analysis of the electrostatic potential. The molecules form zigzag chains in the crystal due to intermolecular C—H…N interactions being electrostatic in origin. The molecules are further stacked due to C—H…O hydrogen bonds. The dispersion component in the total stabilization energy of the crystal lattice is 68.09%.     

Supramolecular interactions in a copper(II) 4′‐(4‐bromophenyl)‐2,2′:6′,2′′‐terpyridine complex

The title compound, [4′‐(4‐bromophenyl)‐2,2′:6′,2′′‐terpyridine]chlorido(trifluoromethanesulfonato)copper(II), [Cu(CF₃O₃S)Cl(C₂₁H₁₄BrN₃)], is a new copper complex containing a polypyridyl‐based ligand. The Cu^II centre is five‐coordinated in a square‐pyramidal manner by one substituted 2,2′:6′,2′′‐terpyridine ligand, one chloride ligand and a coordinated trifluoromethanesulfonate anion. The Cu—N bond lengths differ by 0.1 Å for the peripheral and central pyridine rings [2.032 (2) (mean) and 1.9345 (15) Å, respectively]. The presence of the trifluoromethanesulfonate anion coordinated to the metal centre allows Br...F halogen–halogen interactions, giving rise to the formation of a dimer about an inversion centre. This work also demonstrates that the rigidity of the ligand allows the formation of other types of nonclassical interactions (C—H...Cl and C—H...O), yielding a three‐dimensional network.     

(3aS,7aS)‐1‐{2‐Oxo‐1,3‐bis­[(S)‐1‐phen­ylethyl]­per­hydro‐1,3,2λ5‐benzodi­aza­phosphol‐2‐yl}‐1‐phenylmethanol: a mixture of dia­stereoiso­mers in a disordered crystal

In the title compound, C₂₉H₃₅N₂O₂P, the stereogenic C center α to the P atom, formed during the Pudovik condensation reaction between a deprotonated chiral diaza­phosphole and benz­aldehyde, has disordered substituents, giving a mixture of Cα‐R and Cα‐S diastereoisomers. Moreover, this compound crystallizes with two independent mol­ecules in the asymmetric unit. The observed configuration at the Cα atom is 0.741 (6)‐S mixed with 0.259 (6)‐R, indicating diastereoisomeric enrichment during crystallization. Data from solution and solid‐state studies consistently point to an epimerization process at the Cα atom.     

α‐Halogenoacetanilides as Hydrogen‐Bonding Organocatalysts that Activate Carbonyl Bonds: Fluorine versus Chlorine and Bromine

α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CX_n (n=1–2, X=Cl, Br) or a H?C_Ar bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX₂ interaction.     

[2‐(2‐Pyridyl)‐1H‐benzimidazole‐κ2N2,N3]bis(p‐toluato‐κ2O,O′)manganese(II)

In the title compound, [Mn(C₈H₇O₂)₂(C₁₂H₉N₃)], the manganese(II) centre is surrounded by three bidentate chelating ligands, namely, one 2‐(2‐pyridyl)benzimidazole ligand [Mn—N = 2.1954 (13) and 2.2595 (14) Å] and two p‐toluate ligands [Mn—O = 2.1559 (13)–2.2748 (14) Å]. It displays a severely distorted octahedral geometry, with cis angles ranging from 58.87 (4) to 106.49 (5)°. Intermolecular C—H...O hydrogen bonds between the p‐toluate ligands link the molecules into infinite chains, and every two neighbouring chains are further coupled by N—H...O and C—H...O hydrogen bonds between the 2‐(2‐pyridyl)benzimidazole and p‐toluate ligands, leading to an infinite ribbon‐like double‐chain packing mode. The complete solid‐state structure can be described as a three‐dimensional supramolecular framework, stabilized by these intermolecular hydrogen‐bonding interactions and possible C—H...π interactions, as well as stacking interactions involving the 2‐(2‐pyridyl)benzimidazole ligands.     

N‐tert‐Butyl‐N′‐(5,7‐di­methyl‐1,8‐naphthyridin‐2‐yl)­urea

The title compound, C₁₅H₂₀N₄O, has been synthesized as an AADD recognition unit for quadruple hydrogen bonds. All non‐H atoms of the mol­ecule apart from two methyl groups of the tert‐butyl group lie in a common plane. An intramolecular hydrogen bond is formed connecting two N atoms. In the solid state, the title compound crystallizes as a centrosymmetric dimer connected by N—H?O=C interactions with an N?O distance of 2.824 (2) Å.     

Aurophilicity in Tetraphenylphosphonium 7,8‐Bis(diphenylphosphino)‐7,8‐dicarba‐nido‐undecaborato‐dibromo‐digold(I) [PPh4][{(PPh2)2‐C2B9H10}(AuBr)2]

Reactions of tetraphenylphosphonium dibromoaurate(I) with 1,2‐bis(diphenylphosphino)‐1,2‐dicarba‐closo‐dodecaborane in 2:1 ratio in acetone solution yields brown crystals shown to be the title compound. A single crystal X‐ray study shows coordination of AuBr moieties by the phosphorus atoms of the ligand (Au‐P 2.253(1), 2.246(1); Ag‐Br 2.4041(7), 2.4067(7) Å), permitting a close Au···Au contact (2.9536(3) Å) with concomitant bending of the P‐Au‐Br arrays (173.99(4), 166.14(4)°) and a Br‐Au···Au‐Br torsion of 47.80(2)°.     

Polymeric μ‐bromo‐μ‐pyridine‐3‐carboxyl­ato‐κ3O,O′:N‐mercury(II)

The asymmetric unit of the title polymeric complex, [HgBr(C₆H₄NO₂)]_n or HgBr(nic), contains mercury coordinated via two Br atoms [Hg—Br = 2.6528 (9) and 2.6468 (9) Å], two carboxyl­ate O atoms, which form a characteristic four‐membered chelate ring [Hg—O = 2.353 (6) and 2.478 (7) Å], and an N atom [Hg—N = 2.265 (5) Å], in the form of a very irregular (3+2)‐coordination polyhedron. The pronounced irregularity of the effective Hg (3+2)‐coordination is a result of the rigid stereochemistry of the nicotinate ligand. According to the covalent and van der Waals radii criteria, the strongest bonds are Hg—Br and Hg—N. These covalent interactions form a two‐dimensional poly­mer. The puckered planes are connected by van der Waals interactions, and there are only two intermolecular C—H⋯O hydrogen bonds [3.428 (10) and 3.170 (10) Å].     

Short intermolecular N—Br...O=C contacts in 1,3‐dibromo‐5,5‐dimethylimidazolidine‐2,4‐dione

In the title compound, C₅H₆Br₂N₂O₂, all atoms except for the methyl group lie on a mirror plane in the space group Pnma (No. 62). All bond lengths are normal and the five‐membered ring is planar by symmetry. Two short intermolecular N—Br...O=C contacts [Br...O = 2.787 (2) and 2.8431 (19) Å] are present, originating primarily from the O‐atom lone pairs donating electron density to the antibonding orbitals of the N—Br bonds (delocalization energy transfers 3.27 and 2.11 kcal mol⁻¹). The total stabilization energies of the Br...O interactions are 3.4828 and 2.3504 kcal mol⁻¹.     

An Air‐Stable Semiconducting Polymer Containing Dithieno[3,2‐b:2′,3′‐d]arsole

Arsole‐containing conjugated polymers are a practically unexplored class of materials despite the high interest in their phosphole analogues. Herein we report the synthesis of the first dithieno[3,2‐b;2′,3′‐d]arsole derivative, and demonstrate that it is stable to ambient oxidation in its +3 oxidation state. A soluble copolymer is obtained by a palladium‐catalyzed Stille polymerization and demonstrated to be a p‐type semiconductor with promising hole mobility, which was evaluated by field‐effect transistor measurements.