Decomposition Pathways of Titanium Isopropoxide Ti(OiPr)4: New Insights from UV-Photodissociation Experiments and Quantum Chemical Calculations

Kirill S Ershov; Sergei A Kochubei; Vitaly G Kiselev; Alexey V Baklanov

doi:10.1021/acs.jpca.7b10396

Decomposition Pathways of Titanium Isopropoxide Ti(OⁱPr)₄: New Insights from UV-Photodissociation Experiments and Quantum Chemical Calculations

J Phys Chem A. 2018 Feb 1;122(4):1064-1070. doi: 10.1021/acs.jpca.7b10396. Epub 2018 Jan 19.

Authors

Kirill S Ershov^{1

2}, Sergei A Kochubei³, Vitaly G Kiselev^{1

2

4}, Alexey V Baklanov^{1

2}

Affiliations

¹ Novosibirsk State University , 2, Pirogova Street, 630090 Novosibirsk, Russia.
² Institute of Chemical Kinetics and Combustion , 3, Institutskaya Street, 630090 Novosibirsk, Russia.
³ Institute of Semiconductor Physics , 13, Lavrentyeva Avenue, 630090 Novosibirsk, Russia.
⁴ Semenov Institute of Chemical Physics of the Russian Academy of Sciences , 4, Kosygin Street, 119991 Moscow, Russia.

PMID: 29334730
DOI: 10.1021/acs.jpca.7b10396

Abstract

The UV-photodissociation at 266 nm of a widely used TiO₂ precursor, titanium tetraisopropoxide (Ti(OⁱPr)₄, TTIP), was studied under molecular-beam conditions. Using the MS-TOF technique, atomic titanium and titanium(II) oxide (TiO) were detected among the most abundant photofragments. Experimental results were rationalized with the aid of quantum chemical calculations (DLPNO-CCSD(T) and DFT). Contrary to the existing data in the literature, the new four-centered acetone-elimination reaction was found to be the primary decomposition process of TTIP. According to computational results, the effective activation barrier of this channel was ∼49 kcal/mol, which was ∼13 kcal/mol lower than that of the competing propylene elimination. The former process, followed by the dissociative loss of an H atom, was a dominating channel of TTIP unimolecular decay. The sequential loss of isopropoxy moieties via these two-step processes was supposed to produce the experimentally observed titanium atoms. In turn, the combination of these reactions with propylene elimination can lead to another detected species, TiO. These results indicate that the existing mechanisms of TTIP thermal and photoinitiated decomposition in the chemical-vapor deposition (CVD) of titanium dioxide should be reconsidered.