Infrared Studies of Water in Crystalline Hydrates: K2FeCl5·H2O (Erythrosiderite) and Related Aquopentachloroferrates(III)

1975 ◽  
Vol 53 (1) ◽  
pp. 51-57 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Water Molecule ◽  
Infrared Spectra ◽  
Water Molecules ◽  
High Charge ◽  
Infrared Studies ◽  
Approximate Location ◽  
Crystalline Hydrates

Infrared spectra of M2[FeCl5(H2O)] (M = K, Rb, NH4) at different degrees of deuteration were recorded, between 4000 and 300 cm−1, at 30 and −160 °C. The spectra of the three compounds were closely similar, as was that of natural K2[FeCl5(H2O)] (erythrosiderite). They indicate the existence of only one type of water molecule in the structure. The water molecules are symmetric, well separated from one another, and engage in O—H … Cl bonds with O … Cl distances of about 3.22 Å, as estimated from the OH and OD stretching frequencies. These conclusions support the structure proposed for K2[FeCl5(H2O)] by Bellanca and lead to approximate location of the H atoms. The observed mixing of the librational and translational modes, which occurs when the frequencies of translational modes are high, may be characteristic of H2O molecules coordinated to cations of high charge.

Infrared Studies of Water in Crystalline Hydrates: Sodium Nitroprusside Dihydrate, Na2[Fe(CN)5NO]•2H2O

1971 ◽  
Vol 49 (9) ◽  
pp. 1413-1424 ◽  
Author(s):  
Michaela Holzbecher ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Water Molecule ◽  
Sodium Nitroprusside ◽  
Infrared Spectra ◽  
Structure Determination ◽  
The Other ◽  
Water Molecules ◽  
Infrared Studies ◽  
Increasing Temperature ◽  
Crystalline Hydrates ◽  
The Ideal

Infrared spectra of polycrystalline Na2[Fe(CN)5NO] 2H2O at different degrees of deuteration were studied as a function of temperature. The single peaks observed for the bending fundamentals of isotopically dilute H2O and D2O show that all the water molecules are equivalent, as required by Manoharan and Hamilton's structure determination; the doublets observed for the three fundamentals of isotopically dilute HDO show that the water molecules are asymmetric. Doublet separation decreases gradually with increasing temperature, indicating decreasing asymmetry. The water molecule appears to orient itself so as to maximize the strength of one [Formula: see text] bond, while the other OH group interacts only very weakly with another CN group. The hitherto unknown extent to which the nitroprusside ion deviates from the ideal C4v symmetry has been estimated from the 13C14N stretching spectrum. The 15N16O and 14N18O stretching spectrum was used to confirm that only one type of NO group is present in the crystal, and hence that all nitroprusside ions are equivalent.

Infrared Studies of Water in Crystalline Hydrates: K2CuCl4•2H2O

1974 ◽  
Vol 52 (7) ◽  
pp. 1029-1041 ◽  
Author(s):  
Gwen H. Thomas ◽  
Michael Falk ◽  
Osvald Knop
Keyword(s):  
Crystal Structure ◽  
Water Molecule ◽  
Infrared Spectra ◽  
Vibrational Spectra ◽  
Distinct Type ◽  
Vibrational Coupling ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline K2CuCl4•2H2O at different degrees of deuteration were recorded, between 4000 and 300 cm−1, at temperatures from −160 to 90 °C. The spectra confirm the existence of only one crystallographically distinct type of water molecule in the structure, on sites of symmetry C2r. Vibrational coupling of the bending fundamentals of the water molecule has been analyzed in detail. It is shown that the existence and magnitude of such coupling may be used to predict, from the spectrum of a hydrate, the manner in which a water molecule participates in the crystal structure. The structure and the vibrational spectra of K2CuCl4•2H2O are compared with those of the closely related CuCl2•2H2O.

Infrared Studies of Water in Crystalline Hydrates: LiI.3H2O

1971 ◽  
Vol 49 (3) ◽  
pp. 347-351 ◽  
Author(s):  
George Brink ◽  
Michael Falk
Keyword(s):  
Hydrogen Bond ◽  
Water Molecule ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Infrared Studies ◽  
Librational Motion ◽  
Increasing Temperature ◽  
Crystalline Hydrates

The infrared spectra of undeuterated and partially deuterated LiI.3H2O were recorded between 4000 and 1000 cm−1. The splitting of the fundamentals of isotopically dilute HDO indicates that the water molecules are distorted and form one strong, linear OH … I− hydrogen bond and one weak, non-linear hydrogen bond. The non-equivalence of the two hydrogens of the water molecule disagrees with the space group P63mc − C6υ4 for this hydrate, proposed on the basis of X-ray diffraction studies. It is concluded that the space group, including hydrogens, is one of lower symmetry, P63 − C66. The gradual broadening and convergence of the HDO fundamentals at increasing temperature is explained by increasing librational motion of the water molecules.

Infrared studies of DNA, water, and inositol associations

1968 ◽  
Vol 46 (7) ◽  
pp. 691-695 ◽  
Author(s):  
S. J. Webb ◽  
J. S. Bhorjee
Keyword(s):  
Infrared Spectra ◽  
Water Molecules ◽  
Large Decrease ◽  
Bacterial Dna ◽  
Dichroic Ratio ◽  
Biological Phenomena ◽  
Oriented Films ◽  
Infrared Studies

Ultraviolet and polarized infrared spectra of oriented films of bacterial DNA have been recorded over a range of relative humidities (R.H.) between 10 and 84%. The films were made from a DNA gel in H2O or D2O with and without 5% (w/v) myo-inositol. In the absence of inositol a large decrease in the dichroic ratio at 1670 cm−1 occurred as the R.H. was lowered between 70 and 30%, indicating the occurrence of considerable disorganization. This was not observed when the DNA was dehydrated in the presence of myo-inositol. A marked increase in absorbance at 2600 Å which occurred on lowering the R.H. from 70 to 50% was prevented also by inositol.These results indicate that myo-inositol can replace water molecules and maintain the DNA in the B configuration during dehydration. The possible significance of these observations in the explanation of certain biological phenomena is discussed.

Infrared studies of water in crystalline hydrates: NaClO4•H2O, LiClO4•3H2O, and Ba(ClO4)2•3H2O

1970 ◽  
Vol 48 (13) ◽  
pp. 2096-2103 ◽  
Author(s):  
George Brink ◽  
Michael Falk
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Atom ◽  
Room Temperature ◽  
Water Molecules ◽  
Weak Hydrogen Bond ◽  
Kcal Mole ◽  
Hydrogen Bond Energy ◽  
Weak Hydrogen Bonds ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of undeuterated and partially deuterated NaclO4•H2O, LiClO4•3H2O, and Ba(ClO4)2•3H2O were examined. Crystallographic data point to a weak hydrogen bond between water molecules and the perchlorate ions in LiClO•3H2O. This is confirmed by the high HDO stretching frequencies for this compound. The nearly identical HDO stretching frequencies in LiClO4•3H2O, NaClO4•H2O, Ba(ClO4)2•3H2O, and in aqueous solutions of these salts show that similar weak hydrogen bonds occur in all three hydrates and in solution. The hydrogen bond energy is of the order of 2 kcal/mole. In all three compounds the water molecules are symmetric at room temperature. At −165° the water molecules become highly distorted in the sodium compound, slightly distorted in the barium compound, and remain undistorted in the lithium compound. Very narrow OD stretching bands are observed, showing that the hydrogen atom positions are ordered in all three hydrates.

Raman and Infrared Studies of Hexa-, Tetra-, and Dihydrates of Crystalline Magnesium Nitrate

1973 ◽  
Vol 51 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Tien-Chung Godfrey Chang ◽  
Donald E. Irish
Keyword(s):  
Water Content ◽  
Infrared Spectra ◽  
Magnesium Nitrate ◽  
Octahedral Coordination ◽  
Water Molecules ◽  
Nitrate Ions ◽  
Infrared Studies

Raman and infrared spectra of Mg(NO3)2•6H2O, Mg(NO3)2•6D2O and partially dehydrated products have been obtained and assigned. As the water content is reduced a different set of lines appears and maximizes at the composition Mg(NO3)2 4H2O On further dehydration a third set of lines characteristic of Mg(NO3)2•2H2O appears. The existence of the metastable tetrahydrate had not been confirmed since it was reported in 1932. The spectra suggest that four equatorial sites aroung Mg2+ in the tetrahydrate are occupied by four water molecules and two axial sites by nitrate ions, oriented in monodentate fashion. The spectra suggest that in the dihydrate approximately octahedral coordination is maintained by having two nitrate ions oriented in bidentate fashion and two water molecules trans to each other on the remaining sites.

Infrared Spectra of Water in Crystalline Hydrates: KSnCl3•H2O, an Untypical Monohydrate

1974 ◽  
Vol 52 (16) ◽  
pp. 2928-2931 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Room Temperature ◽  
Water Molecules ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline KSnCl3•H2O were recorded between 4000 and 300 cm−1 at different degrees of deuteration and at temperatures between 30 and −160 °C. At low temperatures the spectra show a complexity indicative of the presence of several crystallographically distinct water molecules. These molecules occupy sites with nearly identical environments and at room temperature are spectroscopically indistinguishable. The environment of each of these molecules is asymmetric. Hydrogen bonds are very weak and probably highly bent. The water molecules are less separated from one another than in K2SnCl4•H2O and may share their potassium neighbors.

Infrared studies of water in crystalline hydrates: K2HgCl4.H2O

1977 ◽  
Vol 55 (10) ◽  
pp. 1736-1744 ◽  
Author(s):  
Michael Falk ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bond ◽  
Neutron Diffraction ◽  
Bond Distance ◽  
Single Type ◽  
Water Molecules ◽  
Dynamic Coupling ◽  
X Ray ◽  
Hydrogen Bond Distance ◽  
Infrared Studies ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline K2HgCl4.H2O at different degrees of deuteration were recorded, in the 4000–250 cm−1 region, at temperatures between liquid-nitrogen and 130 °C. The spectra confirm the existence of a single type of water molecule, engaged in two equivalent hydrogen bonds. The value of 2548 cm−1 for the isolated O—D stretching frequency leads to an estimate of 3.25(3) Å for the O … Cl hydrogen-bond distance, in excellent agreement with the results of X-ray and neutron diffraction. Dynamic coupling is appreciable for stretch, bend, and librational fundamentals but is weaker than in CuCl2.2H2O or K2CuCl4.2H2O, in which the water molecules in the crystal are more tightly bonded.A number of corrected values are reported of isolated O—D stretching frequencies in hydrates studied previously.

Infrared studies of water in crystalline hydrates: gypsum, CaSO4•2H2O

1969 ◽  
Vol 47 (8) ◽  
pp. 1361-1368 ◽  
Author(s):  
V. Seidl ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Hydrogen Bonds ◽  
Isotopic Dilution ◽  
Water Molecules ◽  
Spectral Features ◽  
Vibrational Coupling ◽  
Fundamental Frequencies ◽  
Infrared Studies ◽  
The Difference ◽  
Crystalline Hydrates

Infrared spectra of partially deuterated hydrates yield the fundamental frequencies of isotopically dilute H2O, D2O, and HDO molecules. Isotopic dilution eliminates vibrational coupling and allows the determination of the total number of crystallographically distinct water molecules in the crystal. It also yields the number of distinct symmetric (C2v) and asymmetric (Cs) water molecules. The results for gypsum show that all the water molecules are equivalent and that they are asymmetric, in agreement with crystallographic results. The extent of asymmetry is measured by the difference between the two OH stretching frequencies of HDO molecules, which is 90 cm−1. This corresponds to an estimated difference of 0.02 Å in the [Formula: see text] distances of the two hydrogen bonds. The spectra of partially deuterated gypsum show clearly that spectral features previously explained by the presence of two sets of distinct water molecules or by proton tunnelling, are in fact due to vibrational coupling.

Infrared Studies of Water in Crystalline Hydrates: Location of Hydrogen Atoms and Evidence for a Bifurcated Hydrogen Bond in K2SnCl4•H2O

1974 ◽  
Vol 52 (13) ◽  
pp. 2380-2388 ◽  
Author(s):  
Michael Falk ◽  
Chung-Hsi Huang ◽  
Osvald Knop
Keyword(s):  
Hydrogen Bonding ◽  
Spectral Characteristics ◽  
Supplementary Information ◽  
Water Molecules ◽  
Dynamic Coupling ◽  
Hydrogen Atoms ◽  
Infrared Studies ◽  
Infrared Spectral ◽  
Bifurcated Hydrogen Bond ◽  
Crystalline Hydrates

Infrared spectra of polycrystalline K2SnCl4•H2O at different degrees of deuteration were recorded between 4000 and 300 cm−1 at temperatures between 30 and −160 °C. The spectra are consistent with the crystal structure proposed by Kamenar and Grdenić. The water molecules are all equivalent and asymmetric. They are sufficiently well separated from one another for the dynamic coupling of vibrations to be negligible. Both hydrogens of the water molecule participate in hydrogen bonding; one of the hydrogen bonds is weak and bifurcated. Positional parameters of the hydrogen atoms have been calculated using supplementary information from available n.m.r. studies. Infrared spectral characteristics of water molecules engaged in bifurcated hydrogen bonding are discussed.

Sign in / Sign up

Export Citation Format

Share Document