Effect of interference between anisotropic scattering entities on light scattering from polymer films. II. The correlation function approach

A theory is developed by use of the correlation function approach for calculating both the H_v and V_v intensity of scattered light for a concentrated assembly of spherulities. The scattering becomes a function of the radial and tangential polarizabilities of the spherulite α_r and α_t, the polarizability α_m of the medium, surrounding the spherulites, and the volume fraction ?_s of spherulites. The “effective polarizability of the surroundings” α_s, which appeared in previous theories, becomes function of these variables. The theory can explain, for example, why the V_v scattered intensity passes through a maximum during the course of crystallization.     

Elastomers having high functionality cross links viewed as bimodal networks. An alternative interpretation in terms of bimodal chain-length distributions

Several groups have now prepared poly(dimethylsiloxane) networks of high cross-link functionality by end-linking vinyl-terminated chains by means of Si? H groups in siloxane oligomers (CH₃)₃SiO[SiHCH₃O]_xSi(CH₃)₃. The elongation moduli of these networks were generally found to be considerably larger than the values predicted from the functionality and number density of the cross links (based on the stoichiometry of the end-linking reaction). Not all the Si? H groups in an oligomer are used in the end-linking reaction, however, and the segments between cross-links can themselves act as short network chains. The connectivity of these short chains to the long ones, in what is essentially a bimodal distribution, has been neglected in analyses to date. They are taken into account in the present analysis, giving much better agreement between experiment and theory. The stress-strain behavior for such very short chains can be characterized by the use of Monte Carlo methods and the Fixman-Alben non-Gaussian distribution. This alternative analysis seems useful in reproducing the experimental observations, but further experimental and theoretical will be required to remove some remaining ambiguities. © 1995 John Wiley & Sons, Inc.     

Unitary group approach to spin-adapted open-shell coupled cluster theory

We show that the irreducible tensor operators of the unitary group provide a natural operator basis for the exponential Ansatz which preserves the spin symmetry of the reference state, requires a minimal number of independent cluster amplitudes for each substitution order, and guarantees the invariance of the correlation energy under unitary transformations of core, open-shell, and virtual orbitals. When acting on the closed-shell reference state with n_c doubly occupied and n_v unoccupied (virtual) orbitals, the irreducible tensor operators of the group U(n_c) ? U(n_V) generate all Gelfand-Tsetlin (GT) states corresponding to appropriate irreducible representation of U(n_c + n_v). The tensor operators generating the M-tuply excited states are easily constructed by symmetrizing products of M unitary group generators with the Wigner operators of the symmetric group S_M. This provides an alternative to the Nagel-Moshinsky construction of the GT basis. Since the corresponding cluster amplitudes, which are also U(n_c) ? U(n_s) tensors, can be shown to be connected, the irreducible tensor operators of U(n_c) ? U(n_v) represent a convenient basis for a spin-adapted full coupled cluster calculation for closed-shell systems. For a high-spin reference determinant with n, singly occupied open-shell orbitals, the corresponding representation of U(n), n=n_c + n_v + n_s is not simply reducible under the group U(n_c) ? U(n_s) ? U(n_v). The multiplicity problem is resolved using the group chain U(n) ? U(n_c + n_v) ? U(n_s) ? U(n_c) ?U(n_s)? U(n_v) ? U(n_v). The labeling of the resulting configuration-state functions (which, in general, are not GT states when n_c > 1) by the irreducible representations of the intermediate group U(n_c + n_v) ?U(n_s) turns out to be equivalent to the classification based on the order of interaction with the reference state. The irreducible tensor operators defined by the above chain and corresponding to single, double, and triple substitutions from the first-, second-, and third-order interacting spaces are explicitly constructed from the U(n) generators. The connectedness of the corresponding cluster amplitudes and, consequently, the size extensivity of the resulting spin-adapted open-shell coupled cluster theory are proved using group theoretical arguments. The perturbation expansion of the resulting coupled cluster equations leads to an explicitly connected form of the spin-restricted open-shell many-body perturbation theory. Approximation schemes leading to manageable computational procedures are proposed and their relation to perturbation theory is discussed. © 1995 John Wiley & Sons, Inc.     

Effect of the functionality of junctions on the elasticity of polymacromonomer networks: Computer simulation

The elastic properties of polymer networks formed via the radical polymerization of macromonomers with two polymerizable end groups are studied via computer simulation. It is shown that variation in the average functionality of network junctions, f _avg, in a wide range (∼5–55) leads to a significant change in the shear modulus of the network. According to experiments with real networks (gels of poly(ethylene oxide) macromonomers), the shear modulus increases as f _avg increases. This effect is not due only to a decrease in the fluctuations of positions of network junctions. The main cause of the increase in the modulus is that the modulus component due to interaction between polymer chains (entanglements) increases as the functionality of junctions in the investigated networks increases. The conclusion is made that these networks gain entanglements during the formation of network junctions with high functionality rather than inherit them from the solution of macromonomer chains.     

Schwingungsspektren und Normalkoordinatenanalyse von N-Silylpyrrolen C4H4NSiX3 (X = Cl,CH3, H)

N-trichlorosilyl pyrrole (I) was prepared and, along with N-trimethylsilyl pyrrole (II), investigated by infrared and RAMAN spectroscopy. A normal coordinate analysis which was performed for pyrrole, I, II, and N-silyl pyrrole, suggests that no pure ?SiN stretching frequency”? occurs. This mode is mixed with ν NC₂ and δ(ring) as well as with v_s SiC₃ and v_s SiCl₃ and contributes to frequencies between ～400 and ～1100 cm^?1. The results are compared with quantum chemical calculations for pyrrole and II.     

Hydrolyzed Vinyl Acetate–Divinylbenzene Copolymer Microspheres Containing L -Proline for Chiral Separation of Amino Acids

A new packing material for ligand-exchange chromatography, L -proline-modified hydrolyzed vinyl acetate-divinylbenzene copolymer microspheres, has been prepared and evaluated. The microspheres, prepared by a one-step swelling and polymerization method, have a narrow bead size (as determined by scanning electron microscopy, SEM), a broad pore-size distribution (by nitrogen adsorption) and, especially, inhomogeneous structural composition (by differential scanning calorimetry). The support, which has an L -proline content of 0.35 mmol g^–1 (nitrogen analysis), provides good enantioselectivity and column efficiency. Twenty-three of the twenty-four common D ,L -amino acids tested were resolved on a 250 mm × 4.6 mm i.d. column and mixtures of up to seven racemic amino acids were easily separated into their enantiomers. Two average pore diameters, volume-average (d_v) and surface-average (d_s) pore diameters, are defined. The ratio d_v/d_s is used to characterize the broadness of the pore-size distribution. It is shown that the widely used formula d=4V_p/S for cylindrical pores, where V_p is pore volume and S the specific surface area, gives the surface-average pore diameter.     

Elastomeric properties of end-linked networks of high cross-link functionality. Accounting for possible changes in effective functionality with extent of reaction and chain-length distribution

This study reanalyzes some elastomeric properties in elongation reported for poly(dimethylsiloxane) (PDMS) networks of high cross-link functionality which had been prepared by using multifunctional siloxane oligomers to end link vinyl-terminated PDMS chains. The extent of reaction of the vinyl end groupsP _vi spanned the range of 0.40 to 0.95. These networks had elongation moduli that significantly exceeded the values predicted by the Flory-Erman theory, except at very low values ofP _vi. Trends in their stress-strain isotherms, as characterized by the Mooney-Rivlin constants 2C ₂ and the ratio 2C ₂/C₁, also appeared to be different from those predicted by theory. Neglected in such standard analyses, however, was the fact that the segments between cross-links along the junction precursor molecules can themselves act as short network chains, contributing to the modulus and giving a strongly bimodal distribution of both network chain lengths and cross-link functionalities. Of particular interest is the apparent change in functionality with extent of reaction and chain length distribution. The results thus obtained do suggest strong dependence of the observed values of the phantom modulus on the network chain-length distribution, particularly at very small values of the ratio of the length of the short chains to the long ones. Calculations based on recognition of these complications can be used to characterize more realistically the deformation of such networks. The results give much better agreement with experiment. Such behavior could be an important characteristic of elastomeric networks in general.Also, a preliminary attempt was made to bridge theory with experiment based on Kloczkowski, Mark, and Erman's recent theory of fluctuations of junctions in regular bimodal networks. The agreement between theory and experiment thus obtained is rather satisfactory and lends further support to assumptions that take into account the possibly bimodal nature of these high-functionality networks.     

Extension de la méthode du «logarithme limite» [1] pour la détermination de la composition et de la constante de stabilité des complexes

A study of the conditions of applicability to weak complexes of the relation log x = v log V + log (β_v,cC^c) = f(logV), where V and C are variable and constant total concentrations of the constituants of the complexe, shows that for conditions other than C ? V, another function φ(log V) accounts better for the formation equilibrium of the complexe. From f(log V) and φ (log V) a relation t(log V) is derived whose simple analysis permits the determination of the composition and the stability constant of weak complexes. Applications are given to 1:1, 1:2, 2:2 composition.     

Résonance Magnétique Nucléaire en phase nématique. Exploration de la barrière d'empêchement à la libre rotation pour le fluorure d'acroyle et l'acroléine

The NMR spectrum of acrolein and acroyl fluoride (CH₂?CH? COX with X?H and F) oriented in a nematic phase has been measured and information about conformational equilibrium s-cis ? s-trans has been obtained. The barrier to internal rotation of the COX group has been studied with various hypotheses. Good agreement between experimental and calculated spectra has been obtained using the potential equation V(?) = Σ_nV_n(1 – cos n?)/2, with V₁ = ?200 cal mol^?1, V₂ = 1500 cal mol^?1 and V₃ = 400 cal mol^?1 for the fluorine compound, and V₁ = 1200 cal mol^?1, V₂ = 3000 cal mol^?1 and V₃ = 2000 cal mol^?1 for acrolein; this last compound is found to be mostly in the s-trans conformation.     

CrIII-Phthalocyaninate: Darstellung,Eigenschaften und Kristallstruktur von l-Bis(triphenylphosphin)iminium-trans-di(nitrito(O))phthalocyaninato(2–)-chromat(III)

Cr^III Phthalocyaninates: Synthesis, Properties, and Crystal Structure of l-Bis(triphenylphosphine)iminium trans-Di(nitrito(O))phthalocyaninato(2–)chromate(III) [Cr(H₂O)₂Pc^2?]I_x reacts with excess (PNP)NO₂ in dimethylformamide to yield less soluble greenblack l-bis(triphenylphosphine)iminium trans-di(nitrito(O))phthalocyaninato(2–)chromate(III), ^l(PNP)^trans[Cr(ONO)₂Pc^2?], which crystallizes in the triclinic space group P1 (No. 2) with Z = 2. The Cr atom is in the center of the Pc^2? ligand and the two nitrite ions are monodentate O-coordinated in a mutually trans arrangement to the Cr atom. The Cr? O and Cr? N_iso bond distances are 1.9898(14) und 1.981(2) Å, respectively. The geometric data of the coordinated nitrite ion are: d(N? O) = 1.307(2) Å; d(N? O) = 1.205(2) Å; ?(O? N? O) = 113.7(2)°; ?(Cr? O? N) = 116.85(12)°. The non-bonding O atoms are trans to the Cr atom. The Pc^2? ligand is slightly saddled. Three weak spin-allowed trip-quartet(TQ) transitions (in 10³ cm^?1): TQ1 (8.20) < TQ2 (11.3) < TQ3 (20.33) and the characteristic π-π* transitions of the Pc^2? ligand: B (14.68) < Q₁ (27.1) < Q₂ (29.0) < N (35.4) are observed in the UV-VIS-NIR spectrum. Prominent luminescence spectra are obtained by excitation within the TQ1 region, in which the spin-forbidden trip-sextet transition at 7376 cm^?1 dominates at low temperatures (T < 50 K). The vibrational spectra are discussed. In coincidence of the excitation lines with TQ3, v_s(Cr? O) at 378 cm^?1 is selectively resonance Raman (RR) enhanced. v_as(Cr? O) is observed in the FIR spectrum at 391 cm^?1. The following internal vibrations (in cm^?1) of the nitrito ligand are in the MIR spectrum: v_as(N? O)/1447 > v_as(N? O)/1018/1029 > δ(O? N? O)/828 and in the RR-spectrum: v_s(N? O)/1410 > v_s(N? O)/952, the last followed by three overtones.     

Temperature and pressure dependence of the free volume in the perfluorinated polymer glass CYTOP: A positron lifetime and pressure‐volume‐temperature study

The microstructure of the free volume was studied for an amorphous perfluorinated polymer (T_g = 378 K). To this aim we employed pressure–volume–temperature experiments (PVT) and positron annihilation lifetime spectroscopy (PALS). Using the Simha‐Somcynsky equation of state the hole free volume fraction h and the specific free and occupied volumes, V_f = hV and V_occ = (1 ? h)V, were determined. Their expansivities and compressibilities were calculated from fits of the Tait equation to the volume data. It was found that in the glass V_occ has a particular high compressibility, while the compressibility of V_f is rather low, although h (300 K) = 0.108 is large. In the rubbery state the free volume dominates the total compressibility. From the PALS spectra the hole size distribution, its mean, 〈v_h〉, and mean dispersion, σ_h, were calculated. From a comparison of 〈v_h〉 with V_f a constant hole density of N_h′ = 0.25 × 10²¹ g^?1 was estimated. The volume of the smallest representative freely fluctuating subsystem, 〈V_SV〉 ∝ 1/σ_h², is unusually small. This was explained by an inherent topologic disorder of this polymer. 〈v_h〉 and σ_h show an exponential‐like decrease with increasing pressure P at 298 K. The hole density, calculated from N_h′ = V_f/〈v_h〉, seems to show an increase with P which is unexpected. This was explained by the compression of holes in the glass in two, rather than three, dimensions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2519–2534, 2007     

C68 Fullerene Isomers,Anions, and their Metallofullerenes: Charge‐Stabilizing Different Isomers

The complete set of 6332 classical isomers of the fullerene C₆₈ as well as several non‐classical isomers is investigated by PM3, and the data for some of the more stable isomers are refined by the DFT‐based methods HCTH and B3LYP. C₂:0112 possesses the lowest energy of all the neutral isomers and it prevails in a wide range of temperatures. Among the fullerene ions modeled, C₆₈^2?, C₆₈^4? and C₆₈^6?, the isomers C₆₈^2?(C_s:0064), C₆₈^4?(C_2v:0008), and C₆₈^6?(D₃:0009) respectively, are predicted to be the most stable. This reveals that the pentagon adjacency penalty rule (PAPR) does not necessarily apply to the charged fullerene cages. The vertical electron affinities of the neutral C_s:0064, C_2v:0008, and D₃:0009 isomers are 3.41, 3.29, and 3.10 eV, respectively, suggesting that they are good electron acceptors. The predicted complexation energy, that is, the adiabatic binding energy between the cage and encapsulated cluster, of Sc₂C₂@C₆₈(C_2v:0008) is ?6.95 eV, thus greatly releasing the strain of its parent fullerene (C_2v:0008). Essentially, C₆₈ fullerene isomers are charge‐stabilized. Thus, inducing charge facilitates the isolation of the different isomers. Further investigations show that the steric effect of the encaged cluster should also be an important factor to stabilize the C₆₈ fullerenes effectively.     

Bis(4‐nitraminofurazanyl‐3‐azoxy)azofurazan and Derivatives: 1,2,5‐Oxadiazole Structures and High‐Performance Energetic Materials

Bis(4‐nitraminofurazanyl‐3‐azoxy)azofurazan ( 1 ) and ten of its energetic salts were prepared and fully characterized. Computational analysis based on isochemical shielding surface and trigger bond dissociation enthalpy provide a better understanding of the thermal stabilities for nitramine‐furazans. These energetic compounds exhibit good densities, high heats of formation, and excellent detonation velocity and pressure. Some representative compounds, for example, 1 (v_D: 9541 m s^?1; P: 40.5 GPa), and 4 (v_D: 9256 m s^?1; P: 38.0 GPa) exhibit excellent detonation performances, which are comparable with current high explosives such as RDX (v_D: 8724 m s^?1; P: 35.2 GPa) and HMX (v_D: 9059 m s^?1; P: 39.2 GPa).     

Monomere und dimere Chrom(III)-Phthalocyanine: Synthese und Eigenschaften von Hydroxopyridinophthalocyaninatochrom(III) und μ-Oxodi(pyridinophthalocyaninatochrom(III))

Monomeric and Dimeric Chromium(III) Phthalocyanines: Synthesis and Properties of Hydroxopyridinophthalocyaninatochromium(III) and μ-Oxodi(pyridinophthalocyaninatochromium(III)) Heating of ?[Cr(OH)Pc^2?]”? in pyridine (Py) gives the paramagnetic (T = 273 K) complexes [Cr(OH)(Py)Pc^2?] (μ_Cr = 3.84 μ_B) and [(Cr(Py)Pc^2?)₂O] (μ_Cr = 1.24 μ_B) by consecutive substitution and condensation reactions. The UV-VIS spectra are characterized by the typical B, Q, and N regions of the Pc^2? ligand being shifted hypsochromically for the dimer with respect to the monomer due to excitonic coupling (1.5 kK). Regions of weak absorbance between 8 and 13 resp. 19 kK are assigned to trip-quartet transitions for both complexes. A weak band at 870 cm^?1 in the FIR/MIR spectra is assigned to v_as(Cr? O? Cr). In the resonance Raman(RR) spectra v(Cr? O) at 514 cm^?1 resp. v_s(Cr? O? Cr) at 426 cm^?1 is selectively enhanced. Further strong RR-lines of the μ-Oxo dimer at 110 and 631 cm^?1 are assigned to a (Py? Cr? O)- resp. internal pyridine deformation of a_1g symmetry. An assignment as 2v_as(Cr? O? Cr) is proposed for the remarkable RR line at 1740 cm^?1.     

Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). III. Influence of temperature

Methyl methacrylate (MMA) was polymerized by radical initiation at 0, 25, 50, 75 and 100°C in DMF in the presence of preformed isotactic PMMA (iMA) or preformed syndiotactic PMMA (sMA) with different M?_v and also without preformed PMMA (“blank” polymerizations). From the tacticities of the formed polymers it is concluded that blank polymerization does not conform to simple Bernoulli statistics, but follows at least first-order Markov statistics. The formation of long syndiotactic sequences in the presence of iMA and long isotactic sequences in the presence of sMA denotes still higher-order Markov statistics. The stereoregulating action is improved by higher M?_v of the preformed polymer (matrix) and lower reaction temperature. These influences can be explained by assuming an equilibrium between polymer growth on the matrix and in the “free” solution. For polymerizations in the presence of iMA or sMA below 300°K, the differences in activation enthalpies (ΔH_s/i? – ΔH_i/s?) are practically equal to that for the blank polymerization, ca. 900 cal/mole, whereas the differences in activation entropies (ΔS_s/i? – ΔS_i/s?) differ considerably. (ΔS_s/i? – ΔS_i/s?) values are highly negative in the presence of iMA and highly positive in the presence of sMA. From these results it is concluded that the isotactic and syndiotactic polymer matrices exert a steric influence on the monomer addition process, thus promoting so-called stereospecific replica polymerization.     

Darstellung von trans-[Pt(ox)2X2]2− (X = Cl,Br, I,SCN, OH) durch oxydative Addition an [Pt(ox)2]2− in organischen Solventien

Preparation of trans-[Pt(ox)₂X₂]^2? (X = Cl, Br, I, SCN, OH) by Oxidative Addition to [Pt(ox)₂]^2? in Organic Solvents After extraction of [Pt(ox)₂]^2? with long-chain alkyl-ammonium ions into organic solvents the new Pt^IV complexes trans-[Pt(ox)₂X₂]^2?, X = Cl, Br, I, SCN, OH, are formed directly by oxidative addition. In nonpolar solvents the bulky organic cations prevent the formation of compounds with columnar structure which by partial oxidation in aqueous solution are formed immediately. The IR and Ra spectra of the stable anhydrous (TBA) salts are assigned according to point group D_2h. A characteristical dependence of the C?O, C? O, and Pt? O stretching modes in response to the oxidation state of the central ion is observed. There is vibrational fine structure in the absorption spectrum of [Pt(ox)₂]^2? measured at 10 K with long progressions by coupling of d—d transitions with v_s(Pt? O) and v_s(C?O). The characteristical feature in the UV/VIS spectra of the Pt^IV complexes is caused by intensive π(O, X) ← e_g(Pt) CT transitions.     

Darstellung und spektroskopische Charakterisierung von Di(acido)phthalocyaninatorhodaten(III)

Preparation and Spectroscopical Characterization of Di(acido)phthalocyaninatorhodates(III) Triethylendiaminorhodiumiodide reacts quickly and completely with boiling phthalodinitrile precipitating ?rhodiumphthalocyanine”?, which is purified and dissolved in alkaline media as di(hydroxo)phthalocyaninatorhodate(III). Acidification in the presence of halides or pseudohalides yields less soluble acidophthalocyaninatorhodium reacting with tetra-n-butyl-ammonium(pseudo)halide to give (blue)green tetra-n-butyl-ammoniumdi(acido)phthalocyaninatorhodate(III), (ⁿBu₄N)[Rh(X)₂Pc^2?] (X = Cl, Br, I, N₃, CN, NCO, SCN, SeCN). The asym. Rh? X-stretching vibration (v_as(RhX)) is observed in the f.i.r. at 290 (X = Cl), 233 (Br), 205 (I), 366 (N₃), 347 (CN), 351 (NCO), 257 (SCN) and 214 cm^?1 (SeCN). v_s(RhI) is the only sym. Rh? X-stretching vibration excited at 131 cm^?1 in the Raman spectrum. The m.i.r. and resonance Raman spectra are typical for hexacoordinated phthalocyaninatometalates(III). The influence of the axial ligands is very small. The frequency of the stretching vibrations of the pseudohalo-ligands are as expected (in the case of the ambident ligands the bonding atom is named first): v_as(NN) at 2006 and v_s(NN) at 1270 cm^?1 (N₃); v_as(CN) at 2126 (CN), 2153 (NCO), 2110 (SCN) and 2116 cm^?1 (SeCN). The characteristic π–π*-transitions of the Pc^2?-ligand dominate the UV-vis spectra. The splitting of the Q and N region is discussed and the weak absorbance at ca. 22 kK is assigned to a n–π*-transition.     

Darstellung und Charakterisierung von Bindungsisomeren Bromorhodanorhenaten(IV)

Preparation and characterization of bondisomeric bromorhodanorhenates(IV) The new compounds [ReBr₅(SCN)]^2?, [ReBr₅(NCS)]^2?, cis/tr.-[ReBr₄(NCS)(SCN)]^2?, cis-[ReBr₄(NCS)₂]^2?, mer-[ReBr₃(NCS)₃]^2? are prepared from [ReBr₆]^2? by ligand exchange with NaSCN, KSCN, or (SCN)₂ in organic solvents and isolated by ion exchange chromatography on DEAE cellulose. The bondisomers are significantly distinguished by the frequencies of inner ligand vibrations: v_CN(S) > v_CN(N), v_CS(N) > v_CS(S), δ_NCS δ_SCN. The electronic absorption spectra measured at 10 K exhibit in the region 5700 to 15300 cm^?1 all intraconfigurational transitions (t_2g³) splitted into 8 Kramers doublets by lowered symmetry (C_4v, C_2v, C_s) and spin orbit coupling. The O–O-transitions are deduced form vibrational fine structure and confirmed by electronic Raman bands in some cases. The magnetic moments are in the range of 3.0 to 3.9 B.M.     

Multiple attenuated total internal reflection spectra of ultrathin titanium oxide layers synthesized on a germanium surface

We have realized a vacuum variant for recording the multiple attenuated total internal reflection spectra of ultrathin (2–30 nm) layers of titanium dioxide directly over the course of their synthesis by the molecular lamination method on the surface of germanium single crystals. To a first approximation, there is a linear relationship between the intensity of the bands of the doublet at 890 and 820 cm^–1 (respectivelyv _as andv _s(Ti – O) and the number of molecular lamination cycles (thickness of the synthesized layers); deviations from linearity are due to the effects of the substrate and are expressed in changes in the shape of the contour of the doubletv _as/v _s for thicknesses <10 nm. Redistribution of the intensity in thev _as,v _s bands with an increase in thickness (>20 nm) of the titanium dioxide layer is due to the content of adsorbed H₂O and HCl molecules in the layer, desorption of which when the samples are heated leads to denser packing of the synthesized layers.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 26, No. 2, pp. 251–255, March–April, 1990.     

Étude des spectres infrarouges de divers dialcoyl-diméthoxy-stannanes

The infrared absorption spectra of some dialkyldimethoxystannanes have been investigated in the 400–1500 cm^?1 region. The bands associated with v_s(SnC₂) and v_s(SnO₂) vibrations have been found at 510–521 cm^?1 and 466–475 cm^?1. The group of bands between 560 and 620 cm^?1 is assigned jointly to v_a(SnC₂) and v_a(SnO₂) vibrations. v(C? O) of the methoxy groups linked to tin appears at 1064–1068 cm^?1.