# Vibrational signatures of diamondoid dimers with large intramolecular London dispersion interactions

## TL;DR

This study investigates how large intramolecular London dispersion interactions influence the vibrational properties of diamondoid dimers, revealing new dispersion-induced vibrational modes and structural insights through Raman spectroscopy and DFT analysis.

## Contribution

It provides the first detailed analysis of vibrational signatures of diamondoid dimers affected by strong dispersion interactions using combined experimental and computational methods.

## Key findings

- Identification of new high-energy dispersion-induced vibrational modes.
- Detection of structure-dependent dimer vibrational modes.
- Demonstration of dispersion interactions significantly altering vibrational spectra.

## Abstract

We analyze the vibrational properties of diamondoid compounds via Raman spectroscopy. The compounds are interconnected with carbon-carbon single bonds that exhibit exceptionally large bond lengths up to 1.71 A. Attractive dispersion interactions caused by well-aligned intramolecular H--H contact surfaces determine the overall structures of the diamondoid derivatives. The strong van-der-Waals interactions alter the vibrational properties of the compounds in comparison to pristine diamondoids. Supported by dispersion-corrected density functional theory (DFT) computations, we analyze and explain their experimental Raman spectra with respect to unfunctionalized diamondoids. We find a new set of dispersion-induced vibrational modes comprising characteristic CH/CH$_{2}$ vibrations with exceptionally high energies. Further, we find structure-induced dimer modes that are indicative of the size of the dimers.