Synthesis, Characterization, and Modeling of Naphthyl-Terminated sp Carbon Chains: Dinaphthylpolyynes

TL;DR

This study synthesizes and characterizes dinaphthylpolyynes, revealing their electronic properties and stability, supported by experimental and theoretical methods, advancing understanding of naphthyl-terminated sp carbon chains.

Contribution

It introduces a new synthesis method for dinaphthylpolyynes and combines spectroscopic and modeling techniques to analyze their properties.

Findings

Longest wavelength transition shifts linearly with chain length

DFT-LDA simulations support experimental spectral results

Dinaphthylpolyynes exhibit measurable stability in solid state

Abstract

We report a combined study on the synthesis, spectroscopic characterization and theoretical modelling of a series of {\alpha},{\omega}-dinaphthylpolyynes. We synthesized this family of naphtyl-terminated sp carbon chains by reacting diiodoacetylene and 1-ethynylnaphthalene under the Cadiot-Chodkiewicz reaction conditions. By means of liquid chromatography (HPLC), we separated the products and recorded their electronic absorption spectra, which enabled us to identify the complete series of dinaphthylpolyynes Ar-C2n-Ar (with Ar = naphthyl group and n = number of acetilenic units) with n ranging from 2 to 6. The longest wavelength transition (LWT) in the electronic spectra of the dinaphthylpolyynes red shifts linearly with n away from the LWT of the bare termination. This result is also supported by DFT-LDA simulations. Finally, we probed the stability of the dinaphthylpolyynes in a solid-state precipitate by Fourier-transform infrared spectroscopy and by differential scanning calorimetry (DSC).