TY - JOUR

T1 - Decomposition Pathways of Titanium Isopropoxide Ti(OiPr)4

T2 - New Insights from UV-Photodissociation Experiments and Quantum Chemical Calculations

AU - Ershov, Kirill S.

AU - Kochubei, Sergei A.

AU - Kiselev, Vitaly G.

AU - Baklanov, Alexey V.

PY - 2018/2/1

Y1 - 2018/2/1

N2 - 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.

AB - 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.

KW - THERMAL-DECOMPOSITION

KW - VAPOR-DEPOSITION

KW - TIO2

KW - KINETICS

KW - THERMOCHEMISTRY

KW - PARTICLES

KW - FLAME

KW - FILMS

KW - CVD

UR - http://www.scopus.com/inward/record.url?scp=85041446365&partnerID=8YFLogxK

U2 - 10.1021/acs.jpca.7b10396

DO - 10.1021/acs.jpca.7b10396

M3 - Article

C2 - 29334730

AN - SCOPUS:85041446365

VL - 122

SP - 1064

EP - 1070

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 4

ER -