Longsheng Wang

Trinity College Dublin, Dublin, Leinster, Ireland

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Publications (7)34.52 Total impact

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    ABSTRACT: We describe a series of functionalized N-containing heterosuperbenzenes, created with a view to investigating the strategic role of methoxy substituents in (i) promoting cyclodehydrogenation and (ii) tuning the electronic properties and (iii) the supramolecular order in the resultant fused products.
    Chemical Communications 07/2014; · 6.38 Impact Factor
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    ABSTRACT: A series of sterically encumbered [Pt(L)(σ-acetylide)2 ] complexes were prepared in which L, a dendritic polyaromatic diimine ligand, was held constant (L=1-(2,2'-bipyrid-6-yl)-2,3,4,5-tetrakis(4-tert-butylphenyl)benzene) and the cis ethynyl co-ligands were varied. The optical properties of the complexes were tuned by changing the electronic character, extent of π conjugation and steric bulk of the ethynyl ligands. Replacing electron-withdrawing phenyl-CF3 substituents (4) with electron-donating pyrenes (5) resulted in a red shift of both the lowest-energy absorption (ΔE=3300 cm(-1) , 61 nm) and emission bands (ΔE=1930 cm(-1) , 64 nm). The emission, assigned in each case as phosphorescence on the basis of the excited-state lifetimes, switched from being (3) MMLL'CT-derived (mixed metal-ligand-to-ligand charge transfer) when phenyl/polyphenylene substituents (3, 4, 6) were present, to ligand-centred (3) ππ* when the substituents were more conjugated aromatic platforms [pyrene (5) or hexa-peri-hexabenzocoronene (7)]. The novel Pt(II) acetylide complexes 5 and 7 absorb strongly in the visible region of the electromagnetic spectrum, which along with their long triplet excited-state lifetimes suggested they would be good candidates for use as singlet-oxygen photosensitisers. Determined by in situ photooxidation of 1,5-dihydroxynaphthalene (DHN), the photooxidation rate with pyrenyl-5 as sensitiser (kobs =39.3×10(-3) min(-1) ) was over half that of the known (1) O2 sensitiser tetraphenylporphyrin (kobs =78.6×10(-3) min(-1) ) under the same conditions. Measured (1) O2 quantum yields of complexes 5 and 7 were half and one-third, respectively, of that of TPP, and thus reveal an efficient triplet-triplet energy-transfer process in both cases.
    Chemistry - A European Journal 09/2013; · 5.93 Impact Factor
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    ABSTRACT: AbstractA series of sterically encumbered [Pt(L)(σ‐acetylide)2] complexes were prepared in which L, a dendritic polyaromatic diimine ligand, was held constant (L=1‐(2,2′‐bipyrid‐6‐yl)‐2,3,4,5‐tetrakis(4‐tert‐butylphenyl)benzene) and the cis ethynyl co‐ligands were varied. The optical properties of the complexes were tuned by changing the electronic character, extent of π conjugation and steric bulk of the ethynyl ligands. Replacing electron‐withdrawing phenyl‐CF3 substituents (4) with electron‐donating pyrenes (5) resulted in a red shift of both the lowest‐energy absorption (ΔE=3300 cm−1, 61 nm) and emission bands (ΔE=1930 cm−1, 64 nm). The emission, assigned in each case as phosphorescence on the basis of the excited‐state lifetimes, switched from being 3MMLL′CT‐derived (mixed metal–ligand‐to‐ligand charge transfer) when phenyl/polyphenylene substituents (3, 4, 6) were present, to ligand‐centred 3ππ* when the substituents were more conjugated aromatic platforms [pyrene (5) or hexa‐peri‐hexabenzocoronene (7)]. The novel PtII acetylide complexes 5 and 7 absorb strongly in the visible region of the electromagnetic spectrum, which along with their long triplet excited‐state lifetimes suggested they would be good candidates for use as singlet‐oxygen photosensitisers. Determined by in situ photooxidation of 1,5‐dihydroxynaphthalene (DHN), the photooxidation rate with pyrenyl‐5 as sensitiser (k obs=39.3×10−3 min−1) was over half that of the known 1O2 sensitiser tetraphenylporphyrin (k obs=78.6×10−3 min−1) under the same conditions. Measured 1O2 quantum yields of complexes 5 and 7 were half and one‐third, respectively, of that of TPP, and thus reveal an efficient triplet–triplet energy‐transfer process in both cases.
    Chemistry 01/2013; 19(46). · 5.83 Impact Factor
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    ABSTRACT: This article reports the synthesis and optical properties of three dinuclear, cationic copper complexes [Cu(2)(μ-dppm)(2)(μ-L)](NO(3))(2) (dppm diphenyldiphosphinomethane, L: L(A) 3,6-bis(2-pyridyl)-4,5-diphenyl-pyridazine, L(B) 3,6-bis(2-pyridyl)-4,5-di(4-pyridyl)-pyridazine and L(C) 3,6-bis(2-pyridyl)-8,9-diazafluoranthene). These were formed on the reaction of [Cu(μ-dppm)(NO(3))](2) with a series of N-donor (bppn) ligands L. The single crystal X-ray structures of [Cu(2)(μ-dppm)(2)(μ-L)](NO(3))(2)·CH(2)Cl(2) were determined and revealed that in both, the two copper atoms are held by three bridging ligands, two dppm ligands and one bppn ligand acting as a tetradentate bridge. The absorption spectra of the complexes present a MLCT [Cu → π*(N(∧)N)] band in the λ 370-425 nm region. These new complexes exhibit red-orange MLCT-based emission in the solid-state with lifetimes in the microsecond range. In oxygen-free dichloromethane solution, the complex [Cu(2)(μ-dppm)(2)(μ-L(C))](2+) has a long lifetime of 22.8 μs. The long emission lifetimes are attributed to a rigid conformation that precludes the possible distortion of the copper in the excited state.
    Dalton Transactions 09/2011; 40(33):8320-7. · 4.10 Impact Factor
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    ABSTRACT: This article reports the preparation of a range of phenyl, pyridyl and pyrazinyl substituted pyridazines via the inverse electron demand [2 + 4] Diels-Alder reaction between 3,6-di(2-pyridyl)-1,2,4,5-tetrazines (bptz) and 3,6-di(2-pyrazinyl)-1,2,4,5-tetrazines (bpztz) and suitable dienophiles including acenaphthalene. The resulting polyaromatic compounds vary systematically in the number of aromatic substituents and the number and position of N-heteroatoms. For four of these compounds, the effect of the molecular changes on the solid-state structures were investigated using single crystal X-ray crystallography. The pyridazines were used as bidentate ligands in {M(II)(bipy)(2)} and tris(homoleptic) complexes (M = Fe, Ru). The optical and electrochemical properties of these complexes reflect the electron accepting character of the new ligands. The facial and meridional isomers of the tris complexes could be separated by column chromatography (on silica), thus allowing a spectral comparison of their absorption and emission properties. The solid-state structures of several of the metal complexes are discussed, including that of the facial isomer of the tris Ru(II) complex of 3,6-bis(2-pyridyl)-4,5-bis(4-pyridyl)pyridazine--a potential preformed geometric motif for the predirected construction of supramolecular assemblies.
    Dalton Transactions 08/2011; 40(32):8206-12. · 4.10 Impact Factor
  • Dalton Transactions 02/2011; 40:8206-8212. · 4.10 Impact Factor
  • Dalton Transactions 01/2011; 40:8320-8327. · 4.10 Impact Factor