Structure of 3-methylxanthine

Analysis of Supramolecular Complexes of 3-Methylxanthine with Field Asymmetric Waveform Ion Mobility Spectrometry Combined with Mass Spectrometry

“…A range of noncovalent clusters with different cations are observed in the gas phase, in agreement with Szolomájer et al [10]. When ammonium acetate is added as a solvent modifier, abundant peaks correspond to tetrameric species with alkali metal and ammonium cations ( Figure 1a); for example [(3-MX) 4 [10,12,13] by many singly (Figure 1a), doubly (Figure 1b-d), and multiply (Figure 1d) charged species, making it difficult to identify which species are present because of the overlapping isotopic patterns.…”

“…3-Methylxanthine (3-MX) is an example of a small molecule that can form stable noncovalently bound supramolecular complexes in the gas phase [10]. 3-MX has been shown to selfassemble in the presence of alkali metals and ammonium ions to form clusters around a stabilizing cation, as shown in Structure1; the 3-MX purine base contains both hydrogen bond donor [NH (1) and O(2)) and acceptor (NH(7) and O(6)] groups [11][12][13].…”

Intermolecular N–H...O hydrogen bonds assisted by resonance. Heteroconjugated systems as hydrogen-bond-strengthening functional groups

“…Hydrogen-bond topology: hydrogen-bond connectivities represented by means of: (a) our notation described in the text; (b) EMIl notation (Etter et ai., 1990); (c) EMB notation but taking into account RAHB (Gilli et al, 1989). Mastropaolo, Camerman & Camerman (1991); (k) Ohms, Guth, Hellner, DannOhl & Schweig (1984); (/) Schmalle, H~ggi & Dubler (1988); (m) Prout et al (1994); (n) Ferretti, Bertolasi, Gilli & Borea (1985); (o) Boer (1972); (t7) Bradshaw, Guynn, Wood, Wilson, Dalley & Izatt (1987); (q) Lowe, Schwalbe & Williams (1987); (r) Low, Tollin, Brand & Wilson (1986); (s) Watt, Martin, Duchamp, Mizsak, Nielson & Prairie (1988); (t) Smith, Bobe, Minnetian, Hope & Yanuck (1985). In the remaining examples (7 and 35-39), N.--O distances are rather short (2.734-2.856,~,), although the C:O and NH moieties apparently belong to a O---C--C--NmH non-conjugated moiety.…”

The importance of, and a method for, optimizing the calculation of rotation functions

“…(iv) In the case of 3-methyixanthine (Low, Tollin, Brand & Wilson, 1986), mentioned above as a case where the Patterson-method solution did not routinely refine to a full structural solution, the model obtained from the optimized rotation-function calculation did in fact refine routinely, evidence of a substantive advantage in using the present procedure.…”

“…This problem can be manifest in several ways: (i) in structural determination attempts, on occasion, a fragment can be trapped into a false minimum (Low, Tollin, Brand & Wilson, 1986); (ii) full three-dimensional rotation functions are time consuming and often contain several potential solutions -it is not always possible to examine these adequately; (iii) if further building onto an oriented fragment is to be undertaken, the most precise orientation possible is obviously desirable at each stage -errors can easily proliferate.…”