M\"ossbauer, nuclear inelastic scattering and density functional studies on the second metastable state of Na2[Fe(CN)5NO]$\cdot$2H2O

TL;DR

This study combines M"ossbauer spectroscopy, nuclear inelastic scattering, and density functional theory to analyze the structure and dynamics of the metastable state SII of Na2[Fe(CN)5NO]·2H2O, revealing the NO group's orientation and displacement.

Contribution

It provides a detailed structural and dynamic analysis of the metastable state SII using combined experimental and theoretical methods, highlighting the NO group's orientation and motion.

Findings

NO group in SII adopts a side-on orientation

NO group dynamically displaced between eclipsed conformations

Optimal conditions identified for TMS measurements; NIS conditions need improvement

Abstract

The structure of the light-induced metastable state SII of Na2[Fe(CN)5NO]$\cdot$2H2O 14 was investigated by transmission M\"ossbauer spectroscopy (TMS) in the temperature range 15 between 85 and 135 K, nuclear inelastic scattering (NIS) at 98 K using synchrotron 16 radiation and density functional theory (DFT) calculations. The DFT and TMS results 17 strongly support the view that the NO group in SII takes a side-on molecular orientation 18 and, further, is dynamically displaced from one eclipsed, via a staggered, to a second 19 eclipsed orientation. The population conditions for generating SII are optimal for 20 measurements by TMS, yet they are modest for accumulating NIS spectra. Optimization 21 of population conditions for NIS measurements is discussed and new NIS experiments on 22 SII are proposed.