Infrared spectra of the ammonium ion in crystals. Part VI. Hydrogen bonding in simple and complex ammonium halides

1979 ◽  
Vol 57 (15) ◽  
pp. 2003-2003
Author(s):  
Osvald Knop ◽  
Ian A. Oxton ◽  
Michael Falk
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Ammonium Ion ◽  
Ammonium Halides

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Infrared spectra of the ammonium ion in crystals. Part VI. Hydrogen bonding in simple and complex ammonium halides

1979 ◽  
Vol 57 (4) ◽  
pp. 404-423 ◽  
Author(s):  
Osvald Knop ◽  
Ian A. Oxton ◽  
Michael Falk
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Low Frequency ◽  
Volume Effect ◽  
Ammonium Ion ◽  
Ammonium Halides ◽  
Formal Charge ◽  
Two Factors ◽  
Frequency Branch ◽  
Free Ammonium

The ν1 and ν4bc infrared absorptions of the NH3D+ probe ion dispersed at low concentration in polycrystalline ammonium halides were used to investigate possible correlations between the frequencies of these absorptions and various structural and other parameters of the ammonium compounds. The most important among these parameters are the H … X distance, the acceptor strength of the halogen atom X for hydrogen bonding, and the coordination number C.N. and activation energy Ea for reorientation of the ammonium ion. It is found that the ν1 and ν4bc frequencies are affected by the acceptor strength and by the degree of 'compression' of the ammonium ion in the crystal, the volume effect. These two factors affect ν4bc in the same direction but ν1 in opposite directions. As a consequence, in a ν4bc vs. ν1 plot the halides are separated according to X, C.N., and certain other parameters. The effective radius of the ammonium ion in cubic (NH4)2MX6 is shown to increase with the strength of hydrogen bonding.The Ea vs ν1 plot contains two branches. The low-frequency branch is dominated principally by the strength of the hydrogen bonding and corresponds to C.N. 4 and 8 and to normal hydrogen bonds. The high-frequency branch is dominated principally by the volume effect and corresponds to C.N. 12 and to hydrogen bonds of highly dynamic character (fluxional hydrogen bonds). Ammonium ions with C.N. 6 may correspond to either branch, depending on the formal charge on X. Existence of the so-called symmetrically trifurcated hydrogen bond that has been proposed for the ammonium ion in certain coordinations is not supported by the present evidence.The problem of the fundamental vibrational frequencies of the 'free' ammonium ion is discussed and values are proposed for the 'limiting' ν1. and ν4bc frequencies in ammonium halides. Criteria of hydrogen bonding in ammonium halides are reviewed and comment is offered on symmetry aspects of crystallographic transformations in cubic hexahalometallates(IV), A2MX6.

Infrared spectra of the ammonium ion in crystals. Part XII. Low-temperature transitions in ammonium dichromate, (NH4)2Cr2O7

1982 ◽  
Vol 60 (15) ◽  
pp. 1972-1977
Author(s):  
Gábor Keresztury ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Abundance Ratio ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Hydrogen Bonding Interactions ◽  
Wide Range ◽  
Ammonium Dichromate ◽  
The Difference

Examination of the infrared spectra of the probe ions NH3D+ and NHD3+ in ammonium dichromate confirms the existence of the lowest (Ttr ~ 125 K) of the three transitions that are known, from nonspectroscopic evidence, to occur in this crystal below room temperature. Below Ttr the ammonium ions are of two types, in an abundance ratio of 1:1 and both of symmetry C1. Above Ttr the probe ion spectra are difficult to interpret in detail. The strength of the hydrogen-bonding interactions covers a wide range, as indicated by the difference between the highest and the lowest values of the isotopically isolated ND stretching frequencies at 10 K, 2392 and 2234 cm−1.

Infrared spectra of the ammonium ion in crystals. Part XIV. Hydrogen bonding and orientation of the ammonium ion in fluorides, with observations on the transition temperatures in cubic cryolite, elpasolite, and perovskite halides

1985 ◽  
Vol 63 (12) ◽  
pp. 3328-3353 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk ◽  
Werner Massa
Keyword(s):  
Hydrogen Bonding ◽  
Low Temperature ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Halogen Atom ◽  
Ammonium Ion ◽  
Transition Temperatures ◽  
Coordination Numbers ◽  
Geometric Tolerance ◽  
Ionic Size

The ir spectra of the isotopic probe ion NH3D+ have been used to obtain information about the symmetry, orientation, and hydrogen-bonding involvement of the ammonium ion, between 10 K and room temperature, in NH4F, NH4HF2, (NH4)2[Cr(H2O)6]F5, NH4PF6, (NH4)3SiF7, the elpasolites (NH4)2BFeF6 (B = Na, K) and CS2NH4MF6 (M = Fe, Al), and the cryolites (NH4)3MF6 (M = Al, Cr, Fe). Several of these fluorides exhibit low-temperature transitions, some of which are evident in the probe-ion spectra. It is shown that relating the isotopically isolated ND stretching and bending frequencies to the [Formula: see text] distances and to the coordination numbers of the ammonium ion reveals important trends in the dependence of the behaviour of the ion on its immediate environment in the crystal. A detailed discussion is presented of the effect of ionic size and the geometric tolerance factor t on the transition temperatures of cubic cryolite, perovskite, and elpasolite halides, as well as on the anisotropy of the principal thermal amplitudes of the halogen atom in such compounds. The relation between Ttr and the frequency of the ND stretching absorption of NH3D+ in the ammonium representatives of these classes of halides is also explored.

Infrared Spectra of the Ammonium Ion in Crystals. II. The Ammonium Ion in Trigonal Environments, with a Consideration of Hydrogen Bonding

1975 ◽  
Vol 53 (22) ◽  
pp. 3394-3400 ◽  
Author(s):  
Ian A. Oxton ◽  
Osvald Knop ◽  
Michael Falk
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Isotopic Dilution ◽  
Ammonium Ion ◽  
Ammonium Ions ◽  
Dilution Technique ◽  
Intensity Ratios ◽  
Normal Hydrogen ◽  
Trifurcated Hydrogen Bond

Infrared spectra of polycrystalline (NH4)2GeF6, β-(NH4)2SiF6, and (NH4)2Pb(SO4)2 have been recorded at room and liquid-nitrogen temperatures. The N—D stretching and bending fundamentals of the isotopically dilute NH3D+ ion in these compounds have been studied with particular attention. The occurrence of N—D stretching doublets and bending triplets, of approximate intensity ratios 1:3 and 2:3:3 respectively, confirms the C3v symmetry of the ammonium ion and suggests that the isotopic dilution technique will prove useful as a diagnostic tool for ascertaining site symmetries of the ammonium ion. The spectra are consistent with non-rotating ammonium ions. The frequencies of dilute NH3D+ ions suggest that for the ammonium ion in (NH4)2Pb(SO4)2 a trifurcated hydrogen bond is stronger than a normal hydrogen bond.

Infrared spectra of the ammonium ion in crystals. Part VIII. Spectroscopic criteria of highly-bent hydrogen bonds

1980 ◽  
Vol 58 (9) ◽  
pp. 867-874 ◽  
Author(s):  
Osvald Knop ◽  
Wolfgang J. Westerhaus ◽  
Michael Falk
Keyword(s):  
Low Temperature ◽  
Hydrogen Bonds ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Ammonium Ion ◽  
Temperature Transition ◽  
Increasing Temperature

Available evidence suggests that (1) the stretching frequencies of highly-bent hydrogen bonds decrease with increasing temperature, regardless of whether the bonds are static or dynamic in character, to a single acceptor or to several competing acceptors; and (2) departures from symmetric trifurcation (or bifurcation) toward asymmetric situations lower the stretching frequency. In further support of these criteria isotopic probe ion spectra between 10 K and room temperature have been obtained for taurine and for trigonal (NH4)2MF6 (M = Si, Ge, Sn, Ti). Evidence of a low-temperature transition at 100(10) K in trigonal (NH4)2SnF6 is presented, and existence of the previously reported transition at 38.6 K in trigonal (NH4)2SiF6 is confirmed. Symmetry changes associated with these transitions are discussed.

Hydrogen bonding and conformation in cis- and trans-2-alkoxy-3-hydroxytetrahydrofurans

1968 ◽  
Vol 46 (1) ◽  
pp. 21-24 ◽  
Author(s):  
W. W. Zajac Jr. ◽  
F. Sweet ◽  
R. K. Brown
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectra ◽  
Hydroxyl Absorption ◽  
Cis And Trans ◽  
In Cis ◽  
Infrared Data ◽  
Hydrogen Bonded

Infrared spectra show both free and hydrogen bonded hydroxyl absorption in several trans-2-alkoxy-3-hydroxytetrahydrofurans. The extent of non-bonded hydroxyl is greater than that of bonded hydroxyl. Suggestions are made of possible conformations which might account for the infrared data.

Infrared spectra and hydrogen bonding of pentitols and pyranosides at 20 to 300 K

2000 ◽  
Vol 328 (3) ◽  
pp. 307-319 ◽  
Author(s):  
Mark Rozenberg ◽  
Aharon Loewenschuss ◽  
Yizhak Marcus
Keyword(s):  
Hydrogen Bonding ◽  
Infrared Spectra
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