Novel luminescent homo/heterometallic platinum(ii) alkynyl complexes based on Y-shaped pyridyl diphosphines.

A series of dinuclear platinum(ii) alkynyl complexes [Pt2L2(C[triple bond, length as m-dash]CC6H4R-4)4] (R = H 1, CH32, But3) and unusual tetranuclear Pt(ii)-Ag(i) clusters [Pt2Ag2L(C[triple bond, length as m-dash]CC6H4R-4)6] (R = H, 4; CH3, 5; But, 6), together with novel polymer crystals [Pt2Ag2L(C[triple bond, length as m-dash]CC6H5)6]∞ ([4]∞), were synthesized by a self-assembly reaction between [NBu4]2[Pt(C[triple bond, length as m-dash]CC6H4-R-4)4] and [Ag6L6]6+ (L = 4-(3,5-(diphenylphosphine)phenyl)pyridine). These complexes were characterized by using a range of spectroscopic techniques and complexes 1, 3, 5, and [4]∞ were analysed by X-ray crystallography. Each platinum atom of the Pt(ii)-Ag(i) clusters shows an unusual asymmetric distorted square planar geometry with three alkynyl groups and one bridging L phosphorus atom. Dinuclear complexes 1-3 demonstrate solid-state weak blue luminescence, while tetranuclear Pt(ii)-Ag(i) clusters 4-6 show intense blue-green or yellow-green emission. Furthermore, the crystalline samples of polymer [4]∞ display bright yellow emission (518 nm) that is significantly red-shifted as compared to monomer crystal 4.

Preparation and characterization of maltodextrin-based polyurethane.

Maltodextrin (MD) based polyurethane (MDPU) was prepared by the reaction of MD and polyethyleneglicol (PEG) polyurethane prepolymer (PUP). The structure and properties of the MDPU were investigated by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), Energy dispersive X-ray spectrometry (EDS), and tensile-testing machine in detail. Chemical structure of MDPU was confirmed by FTIR and 1H NMR. MDPU with 66.7% of PUP (MDPU-0.5) was a thermoset plastic with good elasticity but the others (MDPU-1, MDPU-2, and MDPU-3) were thermoplastics. TGA analysis showed that the MDPUs exhibited three stages of the thermal degradation, mainly including urethane linkage (I, 197-268 °C), MD and PUP components (II, 268-380 °C) and the formed stable structures during thermal degradation (III, 400-505 °C), respectively. The various degrees of miscibility were presented. The mechanical properties of thermoplastic MDPUs exhibited relatively high elongation at break under the given relative humidity.

Electrochemiluminescence properties of [Pt2Ag4(C≡CC6H4R)8]n (R = CH3, n = 1; R = H, n = 1 and 2) with amine (TPrA and DBAE) as the coreactant and determination of Sudan I.

Two hexanuclear clusters, [Pt(2)Ag(4)(C≡CC(6)H(4)R)(8)] (R = CH(3), 1; R = H, 2), together with dimer [Pt(2)Ag(4)(C≡CC(6)H(5))(8)](2) (3), have been synthesized and characterized by elemental analyses, electrospray ionization mass spectrometry, and (1)H NMR spectroscopy and by X-ray crystallography for 1 and 3. A considerable enhancement of photoluminescence (PL) and a notable red shift in the emission maximum of 1 (λ(max) 600 nm) relative to 2 (λ(max) 545 nm) are observed. Electrogenerated chemiluminescence (ECL) of 1 and 2 in the absence or presence of coreactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) at different working electrodes in different solvents (CH(2)Cl(2), CH(2)ClCH(2)Cl, or CH(3)CN) has been studied. The ECL spectra are identical with the PL spectra, indicating that ECL emissions are also due to a MLM'CT [Pt(d)/π (C≡CC(6)H(4)R-4) → Pt(p(z))/Ag(sp)/π* (C≡CC(6)H(4)R-4)] state modified by Pt···Ag and Ag···Ag contacts. ECL of 1- and 2/amine systems in CH(2)ClCH(2)Cl was produced at the potentials of 1.14-1.19 V vs SCE, notably negatively shifted by about 0.38 V compared to those of the Ru(bpy)(3)(2+)/amine system. In all cases, ECL quantum efficiencies of 2 are higher than those of 1 and on the same order of magnitude as that of the [Ru(bpy)(3)](PF(6))(2)/amine system. It is noted that Sudan I tends to decrease the ECL intensity of the 1/DBAE system in CH(2)ClCH(2)Cl at a platinum working electrode. A new ECL method for the determination of Sudan I was developed with a linear range of 2.5 × 10(-5)-1.0 × 10(-3) M and a detection limit of 8.0 × 10(-6) M based on 3 times the ratio of signal-to-noise.

Synthesis, structure, photophysical and electrochemiluminescence properties of Re(I) tricarbonyl complexes incorporating pyrazolyl-pyridyl-based ligands.

Three rhenium carbonyl complexes 1-3 were synthesized by reaction of the appropriate bidentate pyrazolyl-pyridyl-based ligand L1, L2 (L1 = 2-[1-{4-(bromomethyl)benzyl}-1H-pyrazol-3-yl]pyridine; L2 = 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene) with [Re(CO)(5)Cl] in toluene. They were characterized by elemental analyses, ESI-MS, (1)H spectroscopy, and X-ray crystallography for 1 and 2. Compounds 1-3 exhibit bright yellow-green luminescence in the solid state and in solution at 298 K with the lifetimes in the microsecond range. It is noteworthy that the luminescent quantum efficiencies of compounds 1-3 are between 0.040 and 0.051, which are much higher than that of the [Re(bpy)(CO)(3)Cl] complex (= 0.019) (M. M. Richter et al., Anal. Chem., 1996, 68, 4370; J. Van Houten et al., J. Am. Chem. Soc., 1976, 98, 4853). Electrogenerated chemiluminescence (ECL) was observed in solutions of these complexes in the absence or presence of coreactant tri-n-propylamine (TPrA) or 2-(dibutylamino)ethanol (DBAE) by stepping the potential of a Pt disk working electrode. The ECL spectra are identical to the photoluminescence spectra, indicating that the chemical reactions following electrochemical oxidation or reduction form the same (3)MLCT excited states as that generated in the photoluminescence experiments. In most cases, the ECL quantum efficiencies of complexes 1-3 are comparable to that of the [Re(L)(CO)(3)Cl] (L = bpy or phen) system. Oxygen tends to substantially decrease ECL intensities of the three rhenium complexes-TPrA system, which could allow them to be used as oxygen sensors.