Spreading and recoil of a surfactant-containing water drop on glass-supported alcohol films

In this paper we report the experimental observation of spreading and recoil of surfactant-containing water drops on various alcohol films supported on glass slides. The time evolution of spreading and recoil behavior was recorded by placing a web camera above the drop. We observed that the drop spread the fastest on CH3OH, followed by C2H5OH, and the slowest on i-PrOH. On the other hand, the recoil behavior was just the opposite. The drop recoiled the slowest on CH3OH and fastest on i-PrOH, while it recoiled in an intermediate time on C2H5OH. In addition, concentration of surfactant in the drop played a prominent role in the spreading and recoil time of the drop, with higher surfactant concentration making the drop spread and recoil faster. The time evolution of spreading velocity of the drop on different alcohol films at various surfactant concentrations occurred with a Gaussian distribution and the peak velocity was reached earliest on CH3OH followed by C2H5OH, while on i-PrOH it took the longest time. The recoil behavior was similar. The variation of velocity as a function of radius exhibited oscillatory behavior, indicating the existence of an interfacial phenomenon. We also report the observation that spreading of the drop occurred without observable fingering instability. Further, we observed by Fourier transform infrared (FTIR) spectroscopic measurements that the drop had mixed with the alcohol films as it spread. Miscibility of the alcohol in the film with the drop, alcohol evaporation cooling-induced temperature gradient, and Marangoni effect probably play important roles in the spreading and recoil behavior of the drop.     

Synthesis,structure, optical and magnetic properties of [CrL(X)3], {L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine; X = Cl,N3, NCS}

Three complexes of composition [CrL(X)₃], where L = 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine and X = Cl⁻, N₃⁻, NCS⁻ are synthesized. They are characterized by IR, UV–Vis, fluorescence, EPR spectroscopic, and X-ray crystallographic studies. Structural studies reveal that the Cr(III) ion is coordinated by three N atoms of L in a meridional fashion. The three anions occupy the other three coordination sites completing the mer-N₃Cl₃ (1) and mer-N₃N₃ (2 and 3), distorted octahedral geometry. The Cr–N2 has a shorter length than the Cr–N1 and Cr–N3 distances and the order Cr–N(NCS⁻) < Cr–N(N₃⁻) < Cr–Cl is observed. They exhibit some of the d–d transitions in the visible and intra-ligand transitions in the UV regions. The lowest energy d–d transition follows the trend [CrLCl₃] < [CrL(N₃)₃] < [CrL(NCS)₃] consistent with the spectrochemical series. In DMF, they exhibit fluorescence having π → π^∗ character. All the complexes show a rhombic splitting as well as zero-field splitting (zfs) in X-band EPR spectra at 77 K.     

Use of HNO(3) as the source of NO to prepare a nitric oxide complex of ruthenium

Reaction of cis-Ru(bisox)(2)Cl(2), where bisox is 4,4,4',4'-tetramethyl-2,2'-bisoxazoline, with HNO(3) in 1 : 4 molar proportion in boiling water under N(2) atmosphere and subsequent addition of an excess of NaClO(4).H(2)O yields [Ru(bisox)(HL)(NO)](ClO(4))(NO(3)) (1). HL is a hydrolysed form of bisox where one of the oxazoline rings opens up. X-Ray crystallography shows that 1 contains an octahedral RuN(5)O core. HL binds the metal through an imino N, an amide N and an alcoholic O atom. Reaction of cis-Ru(bisox)(2)Cl(2) with an excess of NaNO(2) in water gives cis-Ru(bisox)(2)(NO(2))(2) (2). On acidification by HClO(4) in methanol, is smoothly converted to cis-[Ru(bisox)(2)(NO(2))(NO)](ClO(4))(2) (3) due to equilibrium (1). [formula: see text] (1) The X-ray crystal structures of 2 and 3 have also been determined. NO binds Ru in 1 and 3 linearly. The Ru-NO bond length in 1 is 1.764(13) A and that in 3 is approximately 1.78 A. All the three complexes have been characterised by FTIR, NMR and ESIMS. The NO stretching frequencies in 1 and 3 are 1897 and 1936 cm(-1) respectively. While 3 reverts back to 2 readily in presence of OH(-) [equilibrium (1)], 1 does not react with OH(-). It is concluded that while in the reaction of cis-Ru(bisox)(2)Cl(2) with HNO(3), bisox is hydrolysed following abstraction of NO from HNO(3), generation of the nitrosyl complex 3 via reaction (1) is not accompanied with such hydrolysis.     

Concomitant polymorphism of an antiferromagnetically coupled dicopper(II,II) complex with single strand helical assembly: Synthesis,structure, DSC,magnetic and heterogeneous catalytic studies

Two concomitant polymorphic coordination complexes (dark blue – I and black – II) with the formula (Cu₂C₄₄H₆₀N₄O₄) have been synthesized and characterized crystallographically. Magnetic measurements show the presence of a strong antiferromagnetic interaction and the 2J value corresponds extremely well to the theoretically calculated one, indicating the fact that it follows nicely the magneto-structural relationship. Immobilization of the copper(II) complex 1 on a 2D-hexagonal mesoporous silica showed good catalytic efficiency in the liquid phase partial oxidation of olefins in the presence of TBHP as an oxidant.     

Oximato bridged RhIII2MII and RhIIIMI species (MII = Mn, Co, Ni; MI = Cu, Ag)

The reaction of [RhCl₂(HPhL)(PhL)] with M^II(ClO₄)₂·6H₂O in presence of alkali has furnished trinuclear [RhCl₂(PhL)₂]₂M(H₂O)₂·H₂O (HPhL is phenylazobenzaldoxime; M = Mn, Co, Ni). A similar reaction with M^I(PPh₃)₂NO₃ yielded binuclear [RhCl₂(PhL)₂]M(PPh₃)₂ (M = Cu, Ag). In these molecules the oximato group acts as a bridge between Rh^III (bonded at N) and M^II or M^I (bonded at O). In structurally characterized [Rh^IIICl₂(PhL)₂]₂Mn(H₂O)₂.H₂O the centrosymmetric distorted octahedral MnO₆ coordination sphere is spanned by four oximato oxygen atoms and two water molecules lying in trans position. In the lattice the neighbouring molecules are held together by H₂O⋯H₂O⋯H₂O hydrogen bonds generating infinite zigzag chains. The manganese atoms lie parallel to the C-axis, the shortest Mn...Mn distance being 7.992 ?. Magnetic exchange interactions if any are small as seen in room temperature magnetic moments. The manganese system displays a strong EPR signal near g = 2.00. In the complex [RhCl₂(PhL)₂]Cu(PPh₃)₂ the copper atom is coordinated to two oximato oxygen atoms and the two phosphorus atoms in a distorted tetrahedral geometry. The softness of the phosphine ligand is believed to sustain the stable coordination of hard oximato oxygen to soft Cu^I. The coordination sphere of the RhIII atom in both the complexes is uniformly trans-RhN₄Cl₂.     

A unique twisted rod-like pattern due to π-π stacking induced host-guest self-assembly

Here, we reported a unique twisted rod-like nano-architecture of as-synthesized 4-fluorocinnmaoyl chloride derived polynorbornene (PNORCNF) on the addition of 1-pyrenemethanol (PM) as a sensing probe. A significant change in the PNORCNF/PM microenvironment's polarity was observed with increasing PM concentration keeping the solvent (THF) unaltered. The change in polarity could be well documented with the morphological changes of the PNORCNF/PM system. We proposed π-π interaction between PM and cinnamoyl moiety of PNORCNF for this type of well-controlled hierarchical self-aggregation.     

Frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole–poly(vinyl acetate)

The frequency‐dependent conductivity of interpenetrating polymer network composites of polypyrrole (PPy) and poly(vinyl acetate) (PVAc) synthesized by FeCl₃‐impregnated PVAc films being dipped into solutions of pyrrole in water was investigated over a frequency range of 100 Hz to 2 MHz and a temperature range of 110–300 K. For specimens with a PPy content less than the percolation threshold, the quantum mechanical tunneling of electrons was the conduction mechanism. For specimens with a higher PPy content, correlated barrier hopping of electrons appeared to be operative. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1935–1941, 2001     

Unprecedented π···π interaction between an aromatic ring and a pseudo-aromatic ring formed through intramolecular H-bonding in a bidentate Schiff base ligand: crystal structure and DFT calculations

A combination of a single crystal X-ray diffraction study and density functional theory calculations has been applied to a bidentate Schiff base compound to elucidate different cooperative non-covalent interactions involved in the stabilization of the keto form over the enol one in the solid state. The single crystal X-ray structure reveals a remarkable supramolecular assembly of the keto form through a cyclic hydrogen bonded dimeric motif. The most interesting feature in the supramolecular assembly is the formation of a 'dimer of dimer' motif by π···π, CH···π and N···O/O···O interactions in which the π···π interaction involving the aromatic phenyl ring and the intramolecularly hydrogen bonded pseudo-aromatic ring of the keto form lying just above or below the phenyl ring of the other dimer seems to be unprecedented. The optimized geometry of the hydrogen bonded dimeric motif of the keto form of the organic molecule has been obtained by DFT calculations and agrees very well with that found within the crystalline state. The X-ray crystallographic geometry of the 'dimer of dimer' has also been computed, which shows that in the HOMO, the π electrons are localized in the phenyl rings away from each other, while in the LUMO, there is a strong π-π interaction between the phenyl ring of one dimer with the pseudo-aromatic ring of another dimer with an energy estimated to be 7.95 kJ mol(-1). Therefore, on HOMO → LUMO excitation there is localization of π electrons in the central part of the complex moiety which plays a stabilizing role of the dimer of dimer motif in the solid state.     

Telechelic Poly(disulfide)s and Related Block Copolymer

In this communication, a mild, efficient, and generalized polycondensation route is developed for poly(disulfide)s from commercially available monomers 2,2′‐dithiodipyridine and 1,6‐hexanedithiol. Using the stoichiometric imbalance between the two monomers, it is possible to produce telechelic poly(disulfide)s of predictable molecular weight with reactive pyridyl disulfide groups at both the terminals of the chain. The two terminal pyridyl disulfide groups can be quantitatively replaced by a functional thiol using selective thiol‐disulfide exchange and thus produces functional telechelic poly(disulfide)s, which can be used as a macroinitiator to initiate ring‐opening poly­merization of a cyclic lactide monomer generating an ABA‐type triblock copolymer with degradable B block.