The structure and ordering conditions of the self-assembled monolayers (SAMs) of HS(EO)xR, where R ) CH3, EO ) CH2CH2O, and x ) 3-6, on polycrystalline gold (Au) were determined by reflectionabsorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy (EIS). For x ) 5 and 6, RAIRS and SE data show that the 1-thiaoligo(ethylene oxide) [TOEO] segments adopt the highly ordered helical structure of the folded-chain crystal polymorph of crystalline poly(ethylene oxide) and are oriented normal to the substrate. RAIRS and SE data obtained as a function of immersion time show that x ) 6 attains the highly ordered, all helical conformation faster than x ) 5. For x ) 3 and 4, RAIRS and SE data indicate largely disordered structures, with some all-trans conformation but little evidence of the helical conformation. EIS measurements, in an aqueous environment, indicate a significant presence of water in all SAMs with x < 6 while x ) 6 remains essentially free of water and/or ions for extensive periods (2 h). These data suggest that a minimum of five ethylene oxide units are necessary for TOEO SAMs to adopt the helical conformation and that SAMs with x < 6 are penetrated by water or ionic species in an aqueous environment, regardless of the order of the TOEO segment in air.

. Can. J. Chcm. 61. 1516Chcm. 61. (1983. The phenyl sclcnolatcs of tin(ll), Icad(l1). arscnic(lll), antirnony(lll), and bismuth(l1l). M(ScPh),, (M = Sn(ll) or Pb(ll), rr = 2; M = As(ll1). Sb(ll1). or Bi(lll), rr = 3). have been synthcsizccl by acid-base reaction of the appropriate metal acetate (for M = Sn(ll) or Pb(ll)) or thiophcnolatc (for all five clcmcnts) with PhScH. and characterized by clcrncntal analysis and, for the Group V elcmcnts, 77Sc and I3C nnir spectroscopy.M(SPh), and M(ScPh): (M = Sn(l1) or Pb(ll)) arc poorly solublc in McOH but dissolve in the presence of an equimolar or greater amount of P h S or P h S c . The solublc st;unnatc(ll) con~plcxcs arc triligatccl as shown by the slow exchange I1"Sn and, where appropriate. 7 7~c nmr spcctra of the series [Sn(SPh),(ScPh), , I (.r = 0-3) mcasurcd for the supernatant liquor of mixtures in which {Sn(EPh)l),,,,,,l/Pl~E -,,,,;,I > I . The corresponding plumbatc(ll) complcxcs arc pr-obably triligatcd also, but are labile on the nmr timcscalc; the parent complexes P b ( E P h ) havc bccn chmctcrizcd in solution by "I7pb and I3C (E = S and Sc) and 7 7~c (E = Sc) nmr spectroscopy. For both Pb(l1) and Sn(ll), the orclcr of chcmical shifts in the rnctal nmr spcctra is G(MSc3) > 6(MS,). The metal nmr spcctra of the mixturcs M(ScPh),:PhSc :PhS = 1 : 2 : 4 (M = Sn(ll) or Pb(ll)) show that the coordination of P h S c occurs in prcfcrcncc to coordination of P h S fo~. both tin(l1) and Icatl(l1).Thiolatoplurnbatcs(l1) might bc formed during somc antidotal treatments for lead poisoning, so "fingerprint" 2 " 7~b nmr spcctra havc bccn mcasurcd for a rangc of model s o l~~b l c spccics formed in Pb(SR),-(cxccss)RS mixturcs in McOH, including somc mixturcs containing newly synthcsizcd and characterized lead thiolatcs derived from dithiolatc unions. For RS-= MeS-, E t S . PhS-, C h H l l S -(for which "Pb(SR)Z" has bccn shown to bc Pb(SC,Hl1)(OAc)), S ( C H Z ) , S / 2 , -SCH,CHSMc/2. and -SCH,CHS C H~O H ' , 61.1, (from PbMc, in toluene as rcfcrcncc) falls in the conlparativcly short rangc 25 18-2999 pprn.The redistribution of ligands bctwccn M(SPh)> and M(ScPh), in chloroform to give cquilibsium mixtures of M(SPh),(SePh),..., occurs slowly on the preparative timcscalc for M = As, rapidly on the prcp~u.ativc timcscalc but slowly on the "C and 77Sc nmr timcscales for M = Sb, and rapidly on the ' C and 77Sc 111iir tinlcscalcs for M = Bi. Thus 13C and, where appropriate, 7 7~c nnlr data arc reported for M(SPh),(ScPh),+, (M = As or Sb) and Bi(EPh)> ( E = S or Sc). In addition, it has been possible, using I3C nmr assessment of spccics distribution in the systems Sb(SPh),-As(ScPh) and Bi(SPh)3-As(ScPh),, to dcducc that for the trivalent Group V clemcnts the ordcr of prcfcrcncc for PhSc-over PhS-as ligands is Bi > Sb > As.Trends in the I3C nmr data for M ( s P h ) . , ( s~P h )~ , (M = As or Sb) and 77Sc nnlr data for a rangc of metal complcxcs of PhSchavc been discussed. The sclcniurn chemical shifts arc influcnccd primarily by the acceptor atom and asc in the ordcr Cd(ll) ...

Self-assembled monolayers (SAMs) of a series of linear thiols containing a 1-thiaoligo(ethylene oxide) [TOEO] moiety, i.e., HS(CH2CH2O)xCH3, where x = 3 - 6, were prepared on polycrystalline gold (Au) and characterized by reflection absorption infrared spectroscopy (RAIRS) and spectroscopic ellipsometry (SE). For x = 5 and 6, the RAIRS data show that the TOEO segment, oriented normal to the substrate, adopts the highly ordered 7/2 helical structure of the folded-chain crystal polymorph of poly(ethylene oxide). For x = 3 and 4, the RAIRS and SE data indicate disordered, “amorphous” SAMs with essentially no evidence of the helical conformation in the TOEO segment. These data suggest that, for SAMs with TOEO segments, a minimum of five ethylene oxide units is required to adopt a helical conformation.