Structural and Theoretical Evidence of the Depleted Proton Affinity of the N3-Atom in Acyclovir

Anion–Cation Recognition Pattern, Thermal Stability and DFT-Calculations in the Crystal Structure of H2dap[Cd(HEDTA)(H2O)] Salt (H2dap = H2(N3,N7)-2,6-Diaminopurinium Cation)

“…In a private communication to the CSD basis [55] the structure of the salt H3(N1,N7,N9)dapCl2·H2O (see reference code NULCOO in CSD Database) revealed the lesser proton affinity of the N3 atom of Hdap. That seems also agree with the depleted proton affinity found for the N3-atom of acyclovir, a well-known guanine-synthetic nucleoside [52]. The tautomers H2(N1,N3)dap + , H2(N3,N9)dap + and H2(N7,N9)dap + do not have received crystallographic support.…”

“…This review emphasizes the relevance of the N(heterocyclic)-H tautomeric possibilities in neutral and protonated forms of such kinds of natural or synthetic closely related N-heterocyclic ligands. Recent reports from our groups extend these points of view to the guanine-synthetic acyclovir as a ligand [52][53][54]. Now we have the opportunity to deep into the relevance of these factors on the basis of the available crystallographic results related to cationic forms of Hdap, its salts and inner-or out-sphere metal complexes.…”

Metal binding pattern of acyclovir in ternary copper(II) complexes having an S-thioether or S-disulfide NO2S-tripodal tetradentate chelator

“…Surprisingly the crystal structure determination dictated that the 'unusual' asymmetric chelation mode [Cu-N7 2.004(2) and Cu-O6 2.698(2) Å] is favored, a fact attributed to the use of absolute methanol as solvent [12]. Considering the results reported by our research group [21][22][23][24][25] as well as others authors [16][17][18][19][20], one can agree with the idea that the metal binding of acv is very sensitive to the solvent used. In addition, we think that the neutrality or ionic charge of the complex, and obviously the crystal packing forces, is a relevant factor.…”

“…1) but highest chemical stability of its acyclic N9-pendant arm. During the past twenty-five years, Turel [10][11][12][13][14][15], Terrón [16][17][18], Natile [19,20] and we [21][22][23][24][25], became particularly interested in the MBPs of acv, summarized as follows (M = metal ion): (a) the formation of a 'non-assisted' M-N7 bond, (b) the cooperation between a M-N7 bond with an intra-molecular A-HÁ Á ÁO6(acv) interligand interaction (A = coordinated O or N), (c) the N7,O6-chelating mode, (d) l 2 -N7,O(ol) bridging mode, and (e) the unprecedented multifunctional l 3 -N7,O6,O(e),O(ol) mode [25]. These results point towards the attractive possibility of expanding the frontiers of acv coordination [23].…”

Copper(II) polyamine chelates as efficient receptors for acyclovir: syntheses, crystal structures and dft study

“…With the sole exception of the outer-sphere complex (H(N7)acv)trans-[Ru II Cl 4 (O-dmso)(NO)] [3], the acyclovir metal binding patterns (MBP) described in the literature can be summarized as follows (Scheme 2): (MBP-1) Formation of a single M-N7 bond [4][5][6]. (MPB-2) Cooperation between a M-N7(acv) bond and an intramolecular interligand H-bonding interaction type A-HÁ Á ÁO6 (acv), with A = N or O [6][7][8][9][10][11][12][13][14]. A striking case is found in the structure of [Pt(en)(acv) 2 ]SO 4 Á2.5H 2 O [15] where the MBP-1 and MBP-2 modes are both featured in the complex cation.…”