Probing the interaction of Ti clusters with isopropanol for ether production: an experimental and computational study

Abstract

Ti clusters were successfully synthesized in isopropanol using laser ablation in liquid. According to the isotope pattern and the corresponding m/z ratio, the dominant peak is assigned to Ti₅(C₃H₈O)₁₃. Density functional theory (DFT) calculations, are applied to illustrate the interaction of isopropanol with Ti. Among the Ti_n(2−7) clusters, Ti₅ has the highest electrophilicity and chemical potential, justifying the reasonable stability of Ti₅ in forming the experimentally observed Ti₅-C₃H₈O complex. Natural bond orbital analysis shows that the various interactions emanating from σ→ σ* and LP→LP orbitals within the complex contribute to the high stability of the Ti cluster. Moreso, that the Ti—O bond is more of covalent than electrostatic since the Laplacian of electron density for the bond critical point is negative. Finally, the Ti clusters are found to catalyze the coupling of isopropanol to diisopropylether as evidenced from the calculated reaction pathways and high-resolution mass spectrometry analysis. The energy profiles in the reaction coordinates show that the triplet state pathway is the most thermodynamically preferred path. The energy barrier for the Ti₅ pathway are also lower compared to Ti₃ and Ti₇ pathways, showing that the reaction is favorable for Ti₅.