Several different cyclodextrinthiol derivatives have been immobilized on gold surfaces through a chemisorption process to form films which exhibit significantly different features. Three monothiolated cyclodextrin derivatives with different spacers between the cyclodextrin cavity and the thiol group and a mixture of multithiolated cyclodextrins were synthesized and characterized. Chemisorption of these compounds onto gold surfaces gave films which were investigated by Fourier transform infrared (FTIR) spectroscopy, time-of-flight mass spectrometry, contact angle measurements, plasmon surface polariton (PSP) spectroscopy, and cyclic voltammetry. It was found that the chemical structure of each cyclodextrin derivative had a strong influence on the molecular architecture in the resulting films, and in particular on the orientation of the cyclodextrin torus. Models were developed to describe the molecular arrangement in the films.

The photolysis of pyruvic acid vapour has been studied at wavelengths of 366, 345, and 320 nm, at a temperature of 340 K and pressures from about I to 10 Torr. Products observed were COZ and CH3CH0, with the former always in excess, and a quantum yield of COr of 0.9 ? 0. I at 366 nm. Light emission was also observed, and from the effect of added 0, it was concluded that emission occurred from both singlet and triplet states. It is suggested that the primary process in the photolysis is an internal hydrogen-atom transfer followed by dissociation into COz and CH,-C-OH, with the latter then rearranging to give CH3CH0 and other products.The absorption spectrum is reported; the first system begins at about 380 nm, rising to a maximum at about 350 nm, with E,,,,, --10 M-' cm-I, and is attributed to the first excited n* + n+ singlet state. Weak absorption below 300 nm is probably due to the n* + n-state and much stronger absorption below 220 nm to the n* + n state. The thermal decomposition was studied briefly at temperatures from 455 to 584 K and pressures from about 0.8 to 7 Tom. Products were the same as in the photolysis, and Arrhenius parameters of log A (s-I) = 7.19 and E = 27.7 kcal/mol were obtained, based on the formation of COr, which was apparently a simple, homogeneous unimolecular process.S. YAMAMOTO et R. A. BACK. Can. J. Chem. 63, 549 (1985). Optirant a des tempkratures allant de 455 a 584 K et a des pressions allant de 0,8 a 7 Torr, on a britvement CtudiC la dCcomposition thermique. Les produits sont les mCmes que ceux obtenus par photolyse; sur la base de la formation du CO,, qui est apparemment un processus unimolCculaire simple et homogtne, on a aussi obtenue les paramttres dlArrhCnius qui sont: log A (s-I) = 7,19 et E = 27,7 kcal/mol.[Traduit par le journal]

COMMUNICATIONSN M R evidence for a persistent phosphirenyl cation in a compound formulated as (PhiBuC,P)+[B(OSO,CF,)J .f2 '] In 4, the slightly shorter C -C bond length (1.33(3)A) and the elongated P-C bonds (1.78(2)A and 1.82(2)A) would suggest incomplete delocalization when compared with the theoretical models of the free ligand. although the effect of a bound transition metal fragment on the latter is not clear. The Ni-PI bond (2.207(5)A) in 4 lies close to the average Ni-P bond length found by H,tBu2)]. It is noteworthy that in 4 the P 1 atom in the three-membered ring lies closest to P 3 in the five-membered ring, suggesting that the large 'JPp coupling constant between these nuclei may have a through space component similar to that previously observed for [Fe(ti'-P,C,rBu,),] .["I Expcrimentd Procedure 3: Electron beam (400 W) vaporired nickel (0.99 g) \\as cocondensed with an excess of rBiiCP (20 g) at 77 K over a period of 2.5 h. The residue was washed froin the belljar with petroleum ether (40-60 ) and filtered through a celite pad to remove colloidal metal. Removal of solvent i n vacuo afforded a dark oil. Extraction of the oil into petroleum ether (40-60 )followed by chromatographic workup on alumina (4% in:m HzO) with petroleum ether (40 60 ) as eluent afforded 3 as an oil (ca 0.2 g. 3 % ) and 5 (0.2 g. 3 % ) analqtically pure, after recrystalliration from pentane. For spectroscopic data see Tablc 1 . 4 . To [W(C'O),(thf)] generated in situ from [W(CO),] (0.10 g) in THF (25 mL) was added 3 (ca. 0.05 g) and the mixture stirred for 4 h . The solvent was removed in u c u o to yield a dnrk oil. Extraction of the oil into petroleum ether (40-60 ) followed by chromatographic workup on Kieselgel 60 GFL4 with petroleum ether (40-60 ) as eluent allbrded 4 as a microcrystalline powder on removal of mlvent. Recrystallization from pentane (223K) afforded analytically pure 4 (0.05 s. 58%). [23] a) Crystal data for 4 : C2sH,,,N~0,P,W, M =?83.0. triclinic. space group PI (no. 2). (I = 9.415(4), h =12.021(9). c =13.964(4)A. 1 -7X.31(4). /j = 81.66(3).;. = 86.51(5). V = 1 5 3 0 ( I ) A Z , Z = 2 .~)~. ,~~~ =1.70gcm~'.(MoKC) = 46.9 cm-', CAD4: 4241 measured reflections, 3448 observed ( I > 20(1)). K = 0.072. R, = 0.089 (M = l;nz(FJ) for 175 parameters, b) Further details of the crystal structure investigation are available on request from the Director of the Cambridge Crystalloeraphic Data Centre. 12 Union Road, GB-Cambridge CB2 1EW (UK). on quoting thc full journal citation.Self-assembled monolayers (SAMs) of rz-alkanethiols (RSH) on metals have been used both as models for organic surfaces and as modulators of metal surface properties.[" These SAMs are prepared under readily accessible laboratory conditions, and the strong interaction between the metal substrate (Au, Pt. Ag. Cu, Hg. etc.) and the sulfur atom provides a monolayer film that is sufficiently stable to desorption to allow spectroscopic. diffraction, and electrochemical experiments to be performed with a minimum of precautions.['] Crazing-angle FT-IR stud...