Meng-Jiy Wang

Novel Tailoring Reaction for Two Adjacent Coordinated Nitriles Giving Platinum 1,3,5-Triazapentadiene Complexes

The tailoring reaction of the two adjacent nitrile ligands in cis-[PtCl(2)(RCN)(2)] (R = Me, Et, CH(2)Ph, Ph) and [Pt(tmeda)(EtCN)(2)][SO(3)CF(3)](2) (8.(OTf)(2); tmeda = N,N,N,N-tetramethylethylenediamine) upon their interplay with N,N-diphenylguanidine (DPG; NH=C(NHPh)(2)), in a 1:2 molar ratio gives the 1,3,5-triazapentadiene complexes [PtCl(2){NHC(R)NHC(R)=NH}] (1-4) and [Pt(tmeda){NHC(Et)NHC(Et)NH}][SO(3)CF(3)](2) (10.(OTf)(2)), respectively. In contrast to the reaction of 8.(OTf)(2) with NH=C(NHPh)(2), interaction of 8.(OTf)(2) with excess gaseous NH(3) leads to formation of the platinum(II) bis(amidine) complex cis-[Pt(tmeda){NH=C(NH(2))Et}(2)][SO(3)CF(3)](2) (9.(OTf)(2)). Treatment of trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) with 2 equiv of NH=C(NHPh)(2) in EtCN (R = Et) and CH(2)Cl(2) (R = CH(2)Ph, Ph) solutions at 20-25 degrees C leads to [PtCl{NH=C(R)NC(NHPh)=NPh}(RCN)] (11-13). When any of the trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) complexes reacts in the corresponding nitrile RCN with 4 equiv of DPG at prolonged reaction time (75 degrees C, 1-2 days), complexes containing two bidentate 1,3,5-triazapentadiene ligands, i.e. [Pt{NH=C(R)NC(NHPh)=NPh}(2)] (14-16), are formed. Complexes 14-16 exhibit strong phosphorescence in the solid state, with quantum yields (peak wavelengths) of 0.39 (530 nm), 0.61 (460 nm), and 0.74 (530 nm), respectively. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, in agreement with FAB-MS, ESI-MS, IR, and (1)H and (13)C{(1)H} NMR spectra. The structures of 1, 2, 4, 11, 13, 14, 9.(picrate)(2), and 10.(picrate)(2) were determined by single-crystal X-ray diffraction.

A Novel Reactivity Mode for Metal-Activated Dialkylcyanamide Species: Addition of N,N′-Diphenylguanidine to a cis-(R2NCN)2PtII Center Giving an Eight-Membered Chelated Platinaguanidine

The nucleophilic addition of N,N-diphenylguanidine, HN=C(NHPh)(2) (DPG), to two adjacent dialkylcyanamide ligands in cis-[PtCl(2)(NCNR(2))(2)] (R = Me; R(2) = C(5)H(10), C(4)H(8)O) gives unusual eight-membered chelates [PtCl(2){NH=C(NR(2))N(Ph)C(=NH)N(Ph)C(NR(2))=NH}] (1-3) with trisguanidine as the cyclic ligand, in which the central guanidine =NH group remains uncoordinated. Treatment of trans-[PtCl(2)(NCNR(2))(2)] (R = R = Me; R(2) = C(5)H(10), C(4)H(8)O) with 1 equiv of HN=C(NHPh)(2) in a solution (R = R = Me; R(2) = C(5)H(10)) or in a suspension (R(2) = C(4)H(8)O) of CHCl(3) or MeNO(2) at 20-25 degrees C for 20 h results in the generation of the 1,3,5-triazapentadiene monochelates [PtCl{NH=C(NR(2))N(Ph)C(NH(2))=NPh}(NCNR(2))](Cl) (4-6). When any of trans-[PtCl(2)(NCNR(2))(2)] reacts with 2 equiv of DPG at 20-25 degrees C for 1-2 days or 4-6 are treated with 1 equiv more of HN=C(NHPh)(2) at the same temperature, the complexes bearing two chelate rings [Pt{NH=C(NR(2))N(Ph)C(NH(2))=NPh}(2)](Cl)(2) (7-9) are formed. The formulation of the obtained complexes was supported by satisfactory C, H, and N elemental analyses, agreeable ESI(+)-MS, IR and (1)H and (13)C{(1)H} NMR spectroscopies; the structures of 1 and 2 were determined by the single-crystal X-ray diffraction. Theoretical studies (at the B3LYP level of theory) revealed that the alkylnitrile eight-membered product is significantly less stable than the corresponding cyanamide species 1-3, and this fact, at least partially, explains why the former was not detected in the reaction between cis-dinitrileplatinum(II) complexes and DPG.

Dynamic behaviors of droplet impact and spreading: water on five different substrates.

The dynamic wetting behaviors, especially the droplet morphology, of a water droplet impinging on five substrate surfaces were investigated. A water drop was released from 13.6 mm above a solid surface and impinged on substrates. The images (the silhouette and 45 degrees top view) were sequentially recorded from the moment that the droplet impacted the solid surface until it reached equilibrium. The entire profile of each of the water droplets during spreading was obtained from the digitized recorded images. The digitized droplets were then used to detail the spreading mechanism, including information on the relaxations of the wetting diameter, droplet height, contact angle, and spreading velocity. A comparison of the full droplet profiles allows us to clarify the independent motion of two related but independent components, the central region and rim, of an impinging droplet. An interesting plateau region in the droplet height relaxation curve was observed in the first cycle for all substrate surfaces. For hydrophobic surfaces (paraffin and Teflon), three particular growth modes in the droplet height relaxation curve were detected in every oscillation cycle during the early spreading stages. It only took three and four oscillation cycles for a water droplet on the glass and quartz substrates, respectively, to dissipate its energy and reach its equilibrium state. However, it took 72 and 28 oscillation cycles for a water droplet on the Teflon and paraffin substrates, respectively. Moreover, several other new phenomena were also observed.