The resulting polymers are abbreviated as RTZnS in a similar manner with the abbreviation of the monomers. Only OTZnS having the long alkyl chains was soluble in common organic solvents such as THF and chloroform. HTZnS was slightly soluble in DMF, and the other products were insoluble in any common solvents. Plausible reasons for the poor solubility are cross-linking reactions, inherently poor solubility of the zinc complexes, and complexation with ZnO produced as a byproduct (discussed later). Figure 2 Polycondensation of TSH and Zn(OAc) 2 . Table 1 Polycondensation of TSH and Zn(OAc) 2 Run Monomer Yield (%)a M n(M w/M n)b Zn/Sc 1 OTSH 48 7400 (1.4) 0.29 2 BTSH 64 -d 0.40 3 HTSH, 62 -d 0.37 4 IATSH 68 -d 0.45 selleck inhibitor 5 EHTSH

62 -d 0.71 Conditions: TSH 0.200 mmol, Zn(OAc)2 0.300 mmol, dioxane 5.0 mL, 60°C, 24 h, N2. aIsolated yield after precipitation

with methanol. bEstimated by GPC (THF, polystyrene standard). cEstimated using EDX (ratios calculated as averages of ten spots). dNot measurable due to poor solubility. Structural characterization was conducted for OTZnS having enough solubility. The number average molecular weight (M n) was estimated to be 7,400, and the polydispersity index (M w/M n) was relatively narrow. The atom ratio of Zn/S estimated using EDX was 0.29 and almost agrees with the theoretical value AICAR (0.25). The quantitative elemental analysis by EDX was difficult for these powdery polymers, and the Zn/S values in this study may contain 20% to 30% of errors. The 1H-NMR spectrum showed signals at the regions agreeable to the expected structure, but was not selleck products informative enough for the elucidation of the structure due to the broad signals (Figure 3). The 13C-NMR and IR spectra were informative for its structural analysis (Figures 4 and 5). The IR absorption of the SH moieties at 2,564 cm−1 observed in the IR spectrum of OTSH was not

observed in the IR spectrum of OTZnS, suggesting the formation of zinc thiolate structure. The 13C-NMR signals of -SCH2- carbons, -CH2NH-, and C=S carbons were shifted to lower magnetic field region by the transformation of OTSH into OTZnS, GPX6 suggesting the changes in the structure around these moieties, whereas the other signals were observed at identical positions. The -SCH2- carbons in OTSH and OTZnS were observed at 26.4 and 29.4 ppm, respectively. The low-magnetic-field shift from the monomer to the polymer suggests the slight decrease in the electron density. Namely, this result suggests that -ZnSCH2- has a lower electron density than HSCH2-, although the small electronegativity of zinc implies that the zinc atom serves as a stronger electron-donating group than proton. Some 1H-NMR spectroscopic data were reported for zinc thiolates and their original thiols, and the chemical shifts were almost identical or the signals for zinc thiolates were observed at lower magnetic field regions [25, 27]. A plausible reason is the backdonation from the occupied d orbital in zinc.