Rhett C. Smith

Photoluminescence and ion sensing properties of a bipyridyl chromophore-modified semifluorinated polymer and its metallopolymer derivatives

A difluorovinylene aromatic ether polymer (P1) incorporating periodic 5,5′-distyryl-2,2′-bipyridyl units as metal chelating chromophores was prepared by a transition metal-free step-growth polymerization. P1 displays strong ionochromic and ionoluminescent effects in response to transition metals. Although significant emission quenching is observed upon exposure to most transition metal ions, bathochromically shifted emission is observed upon addition of divalent d10 ions (Zn2+, Cd2+ and Hg2+). A selective 10-fold increase in integrated emission intensity is observed upon addition of Zn2+ to P1. The Zn2+-P1 metallopolymer acts as a ratiometric fluorescent indicator selective for fluoride anions, and the Cu2+-P1 metallopolymer exhibits a striking turn-on fluorescence response (>100-fold increase in integrated intensity) selective for cyanide and fluoride anions.

A role for free phosphinidenes in the reaction of magnesium and sterically encumbered ArPCl2 in solution at room temperature

Abstract The reduction of ArPCl 2 (Ar=2,6-Trip 2 C 6 H 3 , 2,6-Mes 2 C 6 H 3 , 2,6-(2,6-Me 2 C 6 H 3 ) 2 C 6 H 3 , or 2,4,6- t Bu 3 C 6 H 3 ) by various forms of activated magnesium have been examined and compared with previously reported reductions using unactivated magnesium. The current reactions are more rapid and give rise to products that are reminiscent of products obtained by irradiation of phosphanylidene-σ 4 -phosphoranes ArPPMe 3 bearing the same Ar groups. The correlation in product distributions suggests the involvement of phosphinidenes in the reduction of aryldichlorophosphines by activated magnesium.

Visible chromophore phosphines as functional elements of luminescent metallopolymers.

A general modular route to fluorophore-linked diphosphines from (4-iodophenyl)P(O)Ph(2) is described. The preparation of chromophoric diphosphine (LHP1) proceeded readily using this route. LHP1 was employed to prepare luminescent metallopolymers of platinum (P1) and palladium (P2) exhibiting modest degrees of polymerization (13-14) and extents of polymerization ( approximately 97%). P1 and P2 appear to be the first metallopolymers polymerized via a visible-absorbing/emitting diphosphine. The photophysical properties of these novel materials are discussed.

A Robust, Reactive, and Remarkably Simple to Prepare Sterically Encumbered meta-Terphenyl Ligand

A cost-efficient, high yield and simple one-pot route to the sterically encumbered iodoterphenyl DcpI [Dcp = 2,6-(2,6-Cl2C6H3)2C6H3] is developed in which the necessary addition of external Grignard reagent is avoided. This material is employed as a convenient precursor to low-coordinate phosphorus compounds, such as DcpP=PDcp (1), DcpP=C(H)Ph (4), and DcpP=PMe3. The resultant aryl is found to provide robust steric protection for 1 and 4 once in place, but reactive intermediates leading to insertion chemistry must be avoided in the course of their synthesis. A new bis(dibenzophosphole) 2 resulting from insertion of a phosphorus atom into vicinal C−Cl bonds was isolated and characterized. The single crystal X-ray structures of 1, 2, and 4 are presented. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Covalently Scaffolded Inter-π-System Orientations in π-Conjugated Polymers and Small Molecule Models.

Organic π-conjugated polymers have emerged as one of the most fascinating classes of materials as they have found utility in a host of plastic electronics technologies. The distance between π-systems and their relative orientation dictate energy/charge transfer, conductivity, and photophysical properties of these materials in bulk. This Feature Article discusses π-conjugated polymers and model compounds in which specific inter-π-system interactions are covalently enforced and the effect that the scaffolding has on optoelectronic properties.

Naphthoxaphospholes as examples of fluorescent phospha-acenes

Seven new fluorescent 2-R-naphtho[2,3-d]oxaphospholes (R-NOPs) (4a–g; R = tBu (a), Ad (b), C(6)H(5) (c), 4-MeC(6)H(4) (d), 4-ClC(6)H(4) (e), 4-BrC(6)H(4) (f ), 4-MeOC(6)H(4) (g)), have been synthesized by cyclocondensation reactions of benzimidoyl chlorides with 3-phosphino-2-naphthol (3). The compounds were characterized by multinuclear NMR, UV-vis, and fluorescence spectroscopy. Compounds 4a–d and 4g were characterized by cyclic voltammetry experiments. The solid state structures of compounds 4b and 4d were also determined by single-crystal X-ray diffraction experiments.

Luminescent phosphonium polyelectrolyte prepared from a diphosphine chromophore: synthesis, photophysics, and layer-by-layer assembly

A luminescent phosphonium-containing polyelectrolyte (P1-OHx) has been prepared by polymerization of a chromophore-containing diphosphine. The resultant cationic polyelectrolyte displays solvatochromism and undergoes facile layer-by-layer assembly with anionic poly(acrylic acid) to form smooth, well-defined films. Solution and film characterization by absorption and photoluminescence spectroscopy, and AFM imaging of films, are reported.

Poly(p-phenylene ethynylene) Incorporating Sterically Enshrouding m-Terphenyl Oxacyclophane Canopies.

A sterically encumbered m-terphenyl oxacyclophane substituted with two aryl iodide substituents has been prepared as a versatile monomer for the preparation of π-conjugated polymers. The monomer has been used to prepare a poly(p-phenylene ethynylene) derivative (P1) incorporating oxacyclophane units as canopies that shield one side of the π-system from inter-chain interactions. The photophysical properties of P1 in dilute solution compare well to those of a poly(p-phenylene ethynylene) derivative (P2) that lacks the canopy. The presence of the steric canopy leads to a diminished inter-chain interaction in the solid state and enhances the kinetic response of P1 to vapors of nitro-organics such as TNT, presumably by increasing the permeability of P1 to these analytes over that of P2.

Solution and film photoluminescence of mesityl-substituted PPVs and low molecular weight models

Poly(p-phenylenevinylene)s and low molecular weight analogues featuring mesityl substituents were prepared and the concentration dependent solution and film absorption and photoluminescent spectroscopic properties of these materials compared to those of less bulky analogues. The presence of bulky mesityl substituents is observed to exert a marked influence on the absorption and photoluminescent properties of these materials by preventing close interchain interactions. A single crystal structure analysis of 1,4-bis(2,6-dimesitylstyryl)-2,5-di-n-hexyloxybenzene (3) shows that despite severe steric crowding, coplanarity (and hence, conjugation) of the distyrylbenzene core is possible.

Bifunctional cross-conjugated luminescent phosphines and phosphine derivatives: phospha-cruciforms

Cross-conjugated bifunctional species including a phosphine, phosphine oxide, phosphine sulfide, phosphonium salt, phosphorus ylide and a gold(I) phosphine complex have been prepared. The photophysical characteristics of the series of compounds have been determined experimentally and are discussed/compared with simpler analogues lacking cross-conjugated branches and rationalized on the basis of DFT calculations.