Tekiz dokuz atomlu germanyum gruplarının ve bunların türevleri olan çoklu ve polimer yapılarının Raman spektroskopiyle incelenmesi

The present study consists of two related parts. The first part is focused on Ramanspectroscopic characterization of neat, en solvated (en = ethylenediamine) or sequestered(sequestering agents: cryptand 2, 2, 2, and 18-crown-6) alkali metal germanium compoundsincluding the well-known monomer deltahedral cluster anions [Ge9]n− (n = 2, 3, 4), as well asoligomer and polymer derivatives of [Ge9]4−; [Ge9-Ge9]6− [45],the condensed[Ge9=Ge9=Ge9]6− [48] and 2−∞[-(Ge9)-] [51], respectively. The assignment of the vibrationalspectra was confirmed by quantum chemical calculations. The monomer [Ge9]n−(n = 2, 3, 4)moieties exhibit very specific band patterns in their Raman spectra, with one very strong andcharacteristic ?breathing mode? at 221 cm−1 (n = 4), 224 cm−1 (n = 2) and 219 cm−1 (n = 3),which may be used as identification sonde, both in solids and liquids. The spectra of thecondensed cluster are characterized by two well-separated frequency groups, located at 268cm-1 (inter) / 220 cm-1 (intra) (dimer), 240 cm-1 / 200 cm-1 (trimer) and 269 cm-1 / 200 cm-1(polimer), respectively. The key for the distinction between inter and intra cluster vibrationsare the intercluster (-Ge9-Ge9-) exobonds which are considerably shorter than those withinthe cluster. Accordingly, the vibrations of the exobonds in all three cluster anions aresignificantly higher than those of the intracluster modes. Also, the downshift of theυ(trimer)inter with respect to the dimer and polymer species is in best agreement with thereported intercluster bond lengths: 2.488 (dimer), 2.579-2.601(trimer) and 2.486 Å (polimer).The cluster compounds and moieties investigated in the present thesis are very sensitive to airand moisture, so that they can only be handled under inert conditions. On the other hand, theirpronounced reactivity makes them potential precursors for the synthesis of new materials. Forthis purpose, several oxidative coupling reactions of [Ge9]4- (precursor K4Ge9) have beenaccomplished utilizing elemental Ge, E15(Ph)3 (E15 = P, As, Sb, Bi; Ph = phenyl), DMF,dodecyltrimetyl ammonium bromide [DoDe]Br, air, water, aqueous HCl solution and NH4Clin liquid ammonia as oxidizing agents. The reaction products and the step-growthcondensation process were followed by Raman spectroscopy, using the measuredcharacteristic frequencies as identification sonde for the different cluster moieties, and powderXRD. Two results are worth mentioning. The Raman spectra have proved that the greencoloration in solutions associated with the oligomerization of the Ge9 cluster originates fromthe presence of the dimer species [Ge9-Ge9]6-. This means that trimer, tetramer and polymercluster anions exist only in the compounds in the solid state. Additionally, both thedecomposition of the precursor K4Ge9 in air, as well its oxidation (protonation) withdeoxygenated water and aqueous solution of HCl yields as main product K3HGe7O16 ⋅ 4H2O.Only when the oxidation takes place in absence of air and water - e.g. with NH4Cl in liquidammonia - the product obtained is the well-known clathrate compound K8Ge46 [18]. This isimportant, since clathrates are known as potential candidates for materials withthermoelectric, HT super conducting and electro optical properties.The second part of the thesis includes the synthesis, crystal structure, Raman and EPR spectraof the novel cluster compound [Na(cp)]3Ge9. The crystal structure (mnkl., Space group:P21/n, a = 22.870(2) Å, b = 14.435(1) Å, c = 24.178(2) Å, β = 107.69(1), Z = 4) contains twotopologically very similar [Ge9]3− moieties with slightly distorted C4v symmetry. Theparamagnetic properties of the cluster ions [Ge9]3− were confirmed by EPR spectroscopy.