Mingfei Zhou

Spectroscopic and Theoretical Studies of Transition Metal Oxides and Dioxygen Complexes

3.1. Sc Group 6772 3.2. Ti Group 6773 3.3. V Group 6775 3.4. Cr Group 6776 3.5. Mn Group 6777 3.6. Fe Group 6779 3.7. Co Group 6780 3.8. Ni Group 6782 3.9. Cu Group 6782 3.10. Zn Group 6784 3.11. Lanthanide Group 6784 3.12. Actinide Group 6785 3.13. Periodic Trends on Bonding and Reactivity 6785 4. Ionic Mononuclear Transition Metal Oxide Species 6787 4.1. Cations 6788 4.2. Anions 6790 4.2.1. Monoxide Anions 6790 4.2.2. Dioxide Anions 6791 4.2.3. Oxygen-Rich Anions 6792 5. Multinuclear Transition Metal Oxide Clusters 6792 5.1. Sc Group 6793 5.2. Ti Group 6793 5.3. V Group 6793 5.4. Cr Group 6797 5.5. Mn Group 6798 5.6. Fe Group 6798 5.7. Co Group 6798 5.8. Ni Group 6798 5.9. Cu Group 6799 6. Summary 6800 7. Acknowledgments 6800 8. References 6800

Probing the intermediates in the MO + CH4 ↔ M + CH3OH reactions by matrix isolation infrared spectroscopy

In this review, we present our recent studies on the MO + CH4 and M + CH3OH model reactions (M = transition metals) in order to provide quantitative information regarding the mechanisms for the catalytic methane-to-methanol conversion process. The reaction intermediates were trapped and probed by matrix isolation infrared absorption spectroscopy. Various important intermediates including OM(CH4), M(CH3OH), CH3MOH, CH3M(O)H and CH3OMH are identified via isotopic substitution experiments in the MO + CH4 and M + CH3OH reactions for selected early and late transition metals. Based on the observed reaction intermediates, some unprecedented reaction pathways are proposed. Complementary quantum chemical calculations support the intermediate identification and help to gain insight into the reaction mechanisms and periodic trends.

Density functional theory study of the B6, B6+, B6−, and B62− clusters

Abstract Bare neutral, cationic, anionic, and dianionic B 6 clusters have been investigated using density functional theory (DFT) method. Eight B 6 , five B 6 + , five B 6 − , and four B 6 2− local minima have been obtained at the B3LYP/6-31+G(d) level of theory. Closed planar or quasi-planar six-membered ring structures ( C 2 h and D 2 h ) are found to be the most stable structures for all the neutral and charged B 6 clusters. Highly delocalized σ bonding as well as π bonding are universal in all the cyclic planar ( C 2 h , D 2 h , C 2 v , and C 2 ); convex ( C 5 v and C s ); and three-dimensional ( O h , D 4 h , and D 2 h ) caged structures.

Infrared spectra and density functional calculations of Cu(CO)1–4+, Cu(CO)1–3, and Cu(CO)1–3− in solid neon

Laser-ablated copper atoms, cations, and electrons react with CO molecules to give binary copper carbony neutral complexes as well as cation and anion complexes, which are isolated in solid neon and argon matrices. Based on isotopic substitution as well as density functional calculations of isotopic frequencies, absorptions at 2234.4, 2230.4, 2211.3, and 2202.1 cm−1 in neon are assigned to C–O stretching vibrations of the linear CuCO+ and Cu(CO)2+, trigonal planar Cu(CO)3+, and tetrahedral Cu(CO)4+ cations. The absorptions at 1746.2, 1793.9, and 1838.9 cm−1 in neon and at 1733.4, 1780.8, and 1829.7 cm−1 in argon are assigned to the linear CuCO− and Cu(CO)2−, and trigonal planar Cu(CO)3− anions, respectively. The solid neon observations of Cu(CO)1–3 are 20–9 cm−1 blue shifted from the argon matrix counterparts, which are in agreement with previous thermal copper atom matrix isolation studies. This work provides the first vibrational spectra of Cu(CO)1–4+ and Cu(CO)1–3−.

Infrared Photodissociation Spectroscopy of Mononuclear Iron Carbonyl Anions

The infrared photodissociation spectroscopy of mass-selected mononuclear iron carbonyl anions Fe(CO)(n)(-) (n = 2-8) were studied in the carbonyl stretching frequency region. The FeCO(-) anion does not fragment when excited with infrared light. Only a single IR active band was observed for the Fe(CO)(2)(-) and Fe(CO)(3)(-) anions, consistent with theoretical predictions that these complexes have linear D(∞h) and planar D(3h) symmetry, respectively. The Fe(CO)(4)(-) anion is the most intense peak in the mass spectra and was characterized to have a completed coordination sphere with high stability. Anion clusters larger than n = 4 were determined to involve a Fe(CO)(4)(-) core anion that is progressively solvated by external CO molecules. Three CO stretching vibrational fundamentals were observed for the Fe(CO)(4)(-) core anion, indicating that the Fe(CO)(4)(-) anion has a C(3v) structure. All the carbonyl stretching frequencies of the Fe(CO)(n)(-) anion complexes are red-shifted with respect to those of the corresponding neutrals.

Infrared spectra and pseudopotential calculations for NUO+, NUO, and NThO in solid neon

The title cation and molecules have been prepared by reactions of laser-ablated metal cations and atoms with NO during condensation in excess neon at 4 K. Infrared fundamentals for the NUO and NThO molecules blue shift 1.6%–2.9% on going from argon to neon matrices and are calculated from 5.8% to 0.0% too high using density functional theory, GAUSSIAN 98, and pseudopotentials on the actinide metal. The isolated NUO+ cation, formed in previous gas-phase ion–molecule reactions, is characterized by new 1118.6 and 969.8 cm−1 neon matrix absorptions. Two normal modes (isotopic frequencies) are accurately modeled by the calculations for NUO+, NUO, and NThO. The isolated NUO+ cation observed here provides a vibrational model for its important isoelectronic UO22+ analog, which has only been characterized in condensed phases where partial neutralization of the dication readily occurs.

Reactions of laser-ablated iron atoms with carbon monoxide: Infrared spectra and density functional calculations of FexCO,Fe(CO)x, and Fe(CO)x−(x=1,2,3) in solid argon

Laser-ablated iron atoms have been reacted with CO molecules during condensation in excess argon. The FeCO molecule is observed at 1922.0 cm−1 in solid argon based on concentration studies, isotopic shifts, and density functional theory frequency calculations; the argon matrix redshifts this band 27.0 cm−1 (1.4%) from the high-resolution gas phase measurement. Absorptions at 1879.2 and 1984.8 cm−1 are assigned from isotopic substitution and density functional theory frequency calculations to the antisymmetric and symmetric vibrations of a bent Fe(CO)2 molecule in the matrix. The Fe(CO)x (x=3,4,5) molecules are also observed on annealing in agreement with earlier matrix work. Iron carbonyl ions were also produced and trapped: photosensitive absorptions at 1770.3, 1721.9, 1815.0, 1786.5, and 1853.5 cm−1 are assigned to FeCO−, Fe(CO)2−, Fe(CO)3−, and Fe(CO)4−, respectively, and a weak photosensitive 2081.5 cm−1 band is assigned to FeCO+. Polynuclear metal carbonyls were also formed on annealing; based on dif...

Carbon Monoxide Bonding With BeO and BeCO3: Surprisingly High CO Stretching Frequency of OCBeCO3

The complexes OCBeCO3 and COBeCO3 have been isolated in a low-temperature neon matrix. The more stable isomer OCBeCO3 has a very high CO stretching mode of 2263 cm(-1) , which is blue-shifted by 122 cm(-1) with respect to free CO and 79 cm(-1) higher than in OCBeO. Bonding analysis of the complexes shows that OCBeO has a stronger OCBeY bond than OCBeCO3 because it encounters stronger π backdonation. The isomers COBeCO3 and COBeO exhibit red-shifted CO stretching modes with respect to free CO. The inverse change of CO stretching frequency in OCBeY and COBeY is explained with the reversed polarization of the σ and π bonds in CO.

Experimental and Theoretical Studies of the Infrared Spectra and Bonding Properties of NgBeCO3 and a Comparison with NgBeO (Ng = He, Ne, Ar, Kr, Xe)

The novel neon complex NeBeCO3 has been prepared in a low-temperature neon matrix via codeposition of laser-evaporated beryllium atoms with O2 + CO/Ne. Doping by the heavier noble gas atoms argon, krypton and xenon yielded the associated adducts NgBeCO3 (Ng = Ar, Kr, Xe). The noble gas complexes have been identified via infrared spectroscopy. Quantum chemical calculations of NgBeCO3 and NgBeO (Ng = He, Ne, Ar, Kr, Xe) using ab initio methods and density functional theory show that the Ng-BeCO3 bonds are slightly longer and weaker than the Ng-BeO bonds. The energy decomposition analysis of the Ng-Be bonds suggests that the attractive interactions come mainly from the Ng → BeCO3 and Ng → BeO σ donation.

Formation and Characterization of the Boron Dicarbonyl Complex [B(CO)2]−

We report the synthesis and spectroscopic characterization of the boron dicarbonyl complex [B(CO)2 ](-) . The bonding situation is analyzed and compared with the aluminum homologue [Al(CO)2 ](-) using state-of-the-art quantum chemical methods.