Gas-Phase Synthesis and Structure of Monomeric ZnOH: A Model Species for Metalloenzymes and Catalytic Surfaces

Abstract

Monomeric ZnOH has been studied for the first time using millimeter and microwave gas-phase spectroscopy. ZnOH is important in surface processes and at the active site of the enzyme carbonic anhydrase. In the millimeter-wave direct-absorption experiments, ZnOH was synthesized by reacting zinc vapor, produced in a Broida-type oven, with water. In the Fourier-transform microwave measurements, ZnOH was produced in a supersonic jet expansion of CH(3)OH and zinc vapor, created by laser ablation. Multiple rotational transitions of six ZnOH isotopologues in their X(2)A' ground states were measured over the frequency range of 22-482 GHz, and splittings due to fine and hyperfine structure were resolved. An asymmetric top pattern was observed in the spectra, showing that ZnOH is bent, indicative of covalent bonding. From these data, spectroscopic constants and an accurate structure were determined. The Zn-O bond length was found to be similar to that in carbonic anhydrase and other model enzyme systems.

Trends in alkali metal hydrosulfides: A combined Fourier transform microwave/millimeter-wave spectroscopic study of KSH ($\tilde X^1 A^\prime $X̃1A′)

“…In contrast, the MOH counterparts are either linear or quasilinear, 16,17 with the exception of CuOH and ZnOH. 18,19 The geometric preference is attributed to the character of the metal-ligand bond. A linear geometry is offered as evidence for a highly ionic metal-ligand bond, while a bent molecular geometry suggests the bond possesses some covalent character.…”

The Fourier transform microwave/millimeter-wave spectrum of YOH and YOD (X̃1Σ+Halfen1, Keogh2, Ziurys3 2015Journal of Molecular Spectroscopy2000View full textAdd to dashboardCite

“…In addition, Table 3 presents the structures of other metal-containing hydroxide species [9,17,21,23,24]. From the table, the OAH bond length in YOH is in close agreement with the linear species RbOH and SrOH.…”

“…Therefore, the OH bond appears to be slightly destabilized in the bent structures as compared to the linear species. Linear MOH species are thought to be more ionic than their bent counterparts [21,24]. The degree of covalent interactions thus appears to increase in the later part of the transition metal series.…”

“…Bond angles of transition metal species have been found to lie in the range 107-114°[e.g. 23,24], very close to that of water at 104.5° [26]. Quasilinear LiOH and MgOH are thought to be intermediate cases: on average linear but exhibiting large amplitude bending motions [21].…”

“…However, very few transition metal hydroxides have been investigated by gas-phase spectroscopic methods. Only CuOH, ZnOH, and AgOH have thus far been studied, mainly by rotational spectroscopy [22][23][24], and YOH has been examined using laser induced fluorescence (LIF) techniques [25]. In contrast to the majority of other hydroxides, the molecules with the late transition metals have been found to be bent, although YOH is linear.…”