Quantum Chemical Topology Study of the Water-Platinum(II) Interaction

Abstract

The "inverse hydration" of neutral complexes of Pt(II) by an axial water molecule, whose one OH-bond is oriented toward Pt, has been the subject of recent works, theoretical as well as experimental. To study the influence of the ligands on this non-conventional H-bond, we extend here our previous energy calculations, using the second-order Moeller-Plesset perturbation theory (MP2) method together with the Dolg-Pélissier pseudopotential for platinum, to various neutral complexes including the well-known chemotherapeutic agent "cisplatin". The stabilization energy, depending on the nature and the configuration of platinum ligands, is dominated by the same important dispersive component, for all the investigated complexes. For a further characterization of this particular H-bond, we used the atoms in molecules theory (AIM) and the topological analysis of the electron localization function (ELF). The charge transfer occurring from the complex to the water molecule and the Laplacian of the density at the bond critical point between water and Pt are identified as interesting AIM descriptors of this non-conventional H-bond. Beyond this AIM analysis, we show that the polarization of the ELF bonding O-H basin involved in the non-conventional H-bond is enhanced during the approach of the water molecule to the Pt complexes. When the water medium, treated in an implicit solvation model, is taken into account, the interaction energies become independent on the nature and configuration of platinum ligands. However, the topological descriptors remain qualitatively unchanged.

Estimation of Transition-Metal Empirical Parameters for Molecular Mechanical Force Fields

“…For this purpose, the RESP charges obtained on the isolated molecules and isolated metal complexes were used supposing that the partial charges remain constant during the rPES scan 21 and reproduce the electrostatic interaction reasonably. This assumption is consistent with the performance of the common MM/MD simulation techniques.…”

Synthesis, Characterization, And Computational Study of Complexes Containing Pt···H Hydrogen Bonding Interactions

“…33 Bergès et al 20 Table 4), thus indicating closed-shell, electrostatic interactions. This same result is also observed in conventional organic hydrogen bonds, 33 in the referred Pt(II)··H-OH interactions 20,21 or in other studies on M···H-X systems 11,34 Nevertheless, and as stated before, 11,33,34 considering the values and signs of  It has been observed that a more negative value of H(r) is related to the decrease in the distance between the interacting atoms, both in certain specific organic hydrogen bonding systems 33,37 and in other non-bonded interactions. 38 In these specific hydrogen bonding systems the donor or proton acceptors are ylides 37 or organic acids, 33 and when known, the X···H distances have been shown to be very short.…”

Preparing Gold(I) for Interactions with Proton Donors: The Elusive [Au]⋅⋅⋅HO Hydrogen Bond

“…[2][3][4] Thef ormer type of association is now well understood at both theoretical and heuristic levels. [5] Although the Pt II ···H interaction in complexes has been confirmed by ac ombination of experimental and theoretical means, [5][6][7] Au···H interactions,p articularly in complexes, cannot be discussed with confidence as yet. Thep roblem is that whereas interactions between proton donors and Au À ions are accepted as genuine hydrogen bonds, [8] most of the Au···H contacts reported in gold(I) complexes are compromised by virtue of concomitantly occurring "classical" hydrogen bonds,c onjugation influences,p referred ligand arrangements or packing effects in crystals that impose positioning of particular H-atoms.…”

“…Taking our cues from comments by Brammer [12] and Martin [13] that am ore negative charge on the metal center would favor stronger hydrogen bonds,w ei nitially embarked on af undamental theoretical investigation to establish the strength of Au···H interactions in known anionic gold(I) complexes with water molecules as compared to those in gaseous Au À adducts;c alculations were also carried out using neutral gold(I) complexes bearing electron-donating ligands as potential proton acceptors.T he results destined as directive for future experimental work, also provide new bonding information and indicate estimates of stabilization achievable by variation of the ligand environment of gold. Theelectronic properties of the auride anion, Au À ,known as astrong proton acceptor in hydrogen bond formation, [3,12] were mimicked by anionic dihydride (1) [14] and dialkyl (2,3,4)complexes [15][16][17] of gold(I) as well as in neutral complexes (5)(6)(7)(8) [18,19] having as trong s-donor N-heterocyclic carbene (NHC) ligand installed at gold.…”