Infrared Photodissociation Spectroscopy and Density Functional Theory Study of Carbon Suboxide Complexes [M(CO)₄(C₃O₂)]⁺ (M = Fe, Co, Ni)

Infrared photodissociation spectra are measured for mass-selected cation complexes with a chemical formula [MC₇O₆]⁺ (M = Fe, Co, Ni) formed via pulsed laser evaporation of metal target in expansions of helium gas seeded by CO. The geometries of the complexes are determined by comparison of the experimental spectra with the simulated spectra from density functional calculations. All of these complexes are identified to have [M­(CO)₄(C₃O₂)]⁺ structures involving a carbon suboxide ligand, which binds the metal center in an η¹ fashion. The antisymmetric CO stretching vibration of C₃O₂ is slightly red-shifted upon coordination. The donor–acceptor bonding interactions between C₃O₂ and the metal centers are analyzed using the EDA-NOCV method. The results show that M ← C₃O₂ σ donation is stronger than the M → C₃O₂ π back-donation in these cation complexes

Infrared Photodissociation Spectroscopic and Theoretical Study of Heteronuclear Transition Metal Carbonyl Cluster Cations in the Gas Phase

Heteronuclear transition metal carbonyl cluster cations FeM­(CO)₈⁺ (M = Co, Ni and Cu) and MCu­(CO)₇⁺ (M = Co and Ni) are produced via a laser vaporization supersonic cluster ion source in the gas phase, which are each mass-selected and studied by infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are established by comparison of the experimental spectra with those derived from density functional theoretical calculations. The FeM­(CO)₈⁺ (M = Co, Ni, Cu) complexes are determined to have eclipsed (CO)₅Fe–M­(CO)₃⁺ structures, and the MCu­(CO)₇⁺ (M = Co, Ni) ions are characterized to have staggered (CO)₄M–Cu­(CO)₃⁺ structures. Natural bonding orbital analysis indicates that the positive charge is mainly distributed on the M­(CO)₃ fragment. The metal–metal interaction involves an σ-type (OC)_4,5M→M­(CO)₃⁺ dative bonding

Infrared Photodissociation Spectroscopy of Heterodinuclear Iron–Zinc and Cobalt–Zinc Carbonyl Cation Complexes

Fe–Zn and Co–Zn heteronuclear carbonyl cation complexes are produced via a laser vaporization supersonic cluster source in the gas phase. The dinuclear FeZn­(CO)₅⁺ and CoZn­(CO)₇⁺ cation complexes are observed to be the most intense heterodinuclear carbonyl cation species in the mass spectra. The infrared spectra are obtained via mass selection and infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Their geometric and electronic structures are assigned with the support of density functional calculations. The FeZn­(CO)₅⁺ complex is determined to have a (OC)₅Fe–Zn structure with a Fe–Zn half bond. The CoZn­(CO)₇⁺ ion is established to have a staggered (OC)₄Co–Zn­(CO)₃ structure involving a Co–Zn σ single bond

Carbon Dioxide Activation by Scandium Atoms and Scandium Monoxide Molecules: Formation and Spectroscopic Characterization of ScCO₃ and OCScCO₃ in Solid Neon

The reactions of carbon dioxide with scandium monoxide molecules and scandium atoms are investigated using matrix isolation infrared spectroscopy in solid neon. The species formed are identified by the effects of isotopic substitution on their infrared spectra as well as density functional calculations. The results show that the ground state ScO molecule reacts with carbon dioxide to form the carbonate complex ScCO₃ spontaneously on annealing. The ground state Sc atom reacts with two carbon dioxide molecules to give the carbonate carbonyl complex OCScCO₃ via the previously reported OScCO insertion intermediate on annealing. The observation of these spontaneous reactions is consistent with theoretical predictions that both the Sc + 2CO₂ → OCScCO₃ and ScO + CO₂ → ScCO₃ reactions are thermodynamically exothermic and are kinetically facile, requiring little or no activation energy

Infrared Photodissociation Spectroscopy of Mass-Selected Silver and Gold Nitrosyl Cation Complexes

The [M­(NO)_<i>n</i>]⁺ cation complexes (M = Au and Ag) are studied for exploring the coordination and bonding between nitric oxide and noble metal cations. These species are produced in a laser vaporization supersonic ion source and probed by infrared photodissociation spectroscopy in the NO stretching frequency region using a collinear tandem time-of-flight mass spectrometer. The geometric and electronic structures of these complexes are determined by comparison of the distinctive experimental spectra with simulated spectra derived from density functional theory calculations. All of these noble metal nitrosyl cation complexes are characterized to have bent NO ligands serving as one-electron donors. The spectrum of [Au­(NO)₂Ar]⁺ is consistent with 2-fold coordination with a near linear N–Au–N arrangement for this ion. The [Au­(NO)_<i>n</i>]⁺ (<i>n</i> = 3–4) cations are determined to be a mixture of 2-fold coordinated form and 3- or 4-fold coordinated form. In contrast, the spectra of [Ag­(NO)_<i>n</i>]⁺ (<i>n</i> = 3–6) provide evidence for the completion of the first coordination shell at <i>n</i> = 5. The high [Au­(NO)_<i>n</i>]⁺ and [Ag­(NO)_<i>n</i>]⁺ (<i>n</i> ≥ 3 for Au, <i>n</i> ≥ 4 for Ag) complexes each involve one or more (NO)₂ dimer ligands, as observed in the copper nitrosyl cation complexes, indicating that ligand–ligand coupling plays an important role in the structure and bonding of noble metal nitrosyl cation complexes

Infrared Photodissociation Spectroscopy of Iron Nitrosyl Cation Complexes: Fe(NO)_<i>n</i>⁺ (<i>n</i> = 1–5)

Infrared spectra of mass-selected mononuclear iron nitrosyl cations Fe­(NO)_<i>n</i>⁺ with <i>n</i> = 1–5 and their argon tagged complexes are measured via infrared photodissociation spectroscopy in the nitrosyl stretching frequency region in the gas phase. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. Two IR active bands were observed for the argon-tagged Fe­(NO)₂⁺ and Fe­(NO)₃⁺ complexes, consistent with theoretical predictions that these complexes have bent <i>C</i>_2<i>v</i> and nonplanar <i>C</i>_3<i>v</i> symmetry, respectively. The Fe­(NO)₄⁺ complex was characterized to have a completed coordination sphere with 17 electrons containing a bent one-electron NO ligand and three three-electron NO ligands. The Fe­(NO)₅⁺ complex was determined to involve a Fe­(NO)₄⁺ core ion that is solvated by an external NO molecule

Table_3_Influence on the fermentation quality, microbial diversity, and metabolomics in the ensiling of sunflower stalks and alfalfa.xlsx

With the rapid development of the livestock industry, finding new sources of feed has become a critical issue that needs to be addressed urgently. China is one of the top five sunflower producers in the world and generates a massive amount of sunflower stalks annually, yet this resource has not been effectively utilized. Therefore, in order to tap into the potential of sunflower stalks for animal feed, it is essential to explore and develop efficient methods for their utilization.In this study, various proportions of alfalfa and sunflower straw were co-ensiled with the following mixing ratios: 0:10, 2:8, 4:6, 5:5, 6:4, and 8:2, denoted as A0S10, A2S8, A4S6, A5S5, A6S4, and A8S2, respectively. The nutrient composition, fermentation quality, microbial quantity, microbial diversity, and broad-spectrum metabolomics on the 60th day were assessed. The results showed that the treatment groups with more sunflower straw added (A2S8, A4S6) could start fermentation earlier. On the first day of fermentation, Weissella spp.dominated overwhelmingly in these two groups. At the same time, in the early stage of fermentation, the pH in these two groups dropped rapidly, which could effectively reduce the loss of nutrients in the early stage of fermentation.In the later fermentation period, a declining trend in acetic acid levels was observed in A0S10, A2S8, and A4S6, while no butyric acid production was detected in A0S10 and A2S8 throughout the process. In A4S6, butyric acid production was observed only after 30 days of fermentation. From the perspective of metabolites, compared with sunflower ensiling alone, many bioactive substances such as flavonoids, alkaloids, and terpenes are upregulated in mixed ensiling.</p

Table_2_Influence on the fermentation quality, microbial diversity, and metabolomics in the ensiling of sunflower stalks and alfalfa.xlsx

With the rapid development of the livestock industry, finding new sources of feed has become a critical issue that needs to be addressed urgently. China is one of the top five sunflower producers in the world and generates a massive amount of sunflower stalks annually, yet this resource has not been effectively utilized. Therefore, in order to tap into the potential of sunflower stalks for animal feed, it is essential to explore and develop efficient methods for their utilization.In this study, various proportions of alfalfa and sunflower straw were co-ensiled with the following mixing ratios: 0:10, 2:8, 4:6, 5:5, 6:4, and 8:2, denoted as A0S10, A2S8, A4S6, A5S5, A6S4, and A8S2, respectively. The nutrient composition, fermentation quality, microbial quantity, microbial diversity, and broad-spectrum metabolomics on the 60th day were assessed. The results showed that the treatment groups with more sunflower straw added (A2S8, A4S6) could start fermentation earlier. On the first day of fermentation, Weissella spp.dominated overwhelmingly in these two groups. At the same time, in the early stage of fermentation, the pH in these two groups dropped rapidly, which could effectively reduce the loss of nutrients in the early stage of fermentation.In the later fermentation period, a declining trend in acetic acid levels was observed in A0S10, A2S8, and A4S6, while no butyric acid production was detected in A0S10 and A2S8 throughout the process. In A4S6, butyric acid production was observed only after 30 days of fermentation. From the perspective of metabolites, compared with sunflower ensiling alone, many bioactive substances such as flavonoids, alkaloids, and terpenes are upregulated in mixed ensiling.</p

Table_4_Influence on the fermentation quality, microbial diversity, and metabolomics in the ensiling of sunflower stalks and alfalfa.xlsx

With the rapid development of the livestock industry, finding new sources of feed has become a critical issue that needs to be addressed urgently. China is one of the top five sunflower producers in the world and generates a massive amount of sunflower stalks annually, yet this resource has not been effectively utilized. Therefore, in order to tap into the potential of sunflower stalks for animal feed, it is essential to explore and develop efficient methods for their utilization.In this study, various proportions of alfalfa and sunflower straw were co-ensiled with the following mixing ratios: 0:10, 2:8, 4:6, 5:5, 6:4, and 8:2, denoted as A0S10, A2S8, A4S6, A5S5, A6S4, and A8S2, respectively. The nutrient composition, fermentation quality, microbial quantity, microbial diversity, and broad-spectrum metabolomics on the 60th day were assessed. The results showed that the treatment groups with more sunflower straw added (A2S8, A4S6) could start fermentation earlier. On the first day of fermentation, Weissella spp.dominated overwhelmingly in these two groups. At the same time, in the early stage of fermentation, the pH in these two groups dropped rapidly, which could effectively reduce the loss of nutrients in the early stage of fermentation.In the later fermentation period, a declining trend in acetic acid levels was observed in A0S10, A2S8, and A4S6, while no butyric acid production was detected in A0S10 and A2S8 throughout the process. In A4S6, butyric acid production was observed only after 30 days of fermentation. From the perspective of metabolites, compared with sunflower ensiling alone, many bioactive substances such as flavonoids, alkaloids, and terpenes are upregulated in mixed ensiling.</p

Table_1_Influence on the fermentation quality, microbial diversity, and metabolomics in the ensiling of sunflower stalks and alfalfa.xlsx

With the rapid development of the livestock industry, finding new sources of feed has become a critical issue that needs to be addressed urgently. China is one of the top five sunflower producers in the world and generates a massive amount of sunflower stalks annually, yet this resource has not been effectively utilized. Therefore, in order to tap into the potential of sunflower stalks for animal feed, it is essential to explore and develop efficient methods for their utilization.In this study, various proportions of alfalfa and sunflower straw were co-ensiled with the following mixing ratios: 0:10, 2:8, 4:6, 5:5, 6:4, and 8:2, denoted as A0S10, A2S8, A4S6, A5S5, A6S4, and A8S2, respectively. The nutrient composition, fermentation quality, microbial quantity, microbial diversity, and broad-spectrum metabolomics on the 60th day were assessed. The results showed that the treatment groups with more sunflower straw added (A2S8, A4S6) could start fermentation earlier. On the first day of fermentation, Weissella spp.dominated overwhelmingly in these two groups. At the same time, in the early stage of fermentation, the pH in these two groups dropped rapidly, which could effectively reduce the loss of nutrients in the early stage of fermentation.In the later fermentation period, a declining trend in acetic acid levels was observed in A0S10, A2S8, and A4S6, while no butyric acid production was detected in A0S10 and A2S8 throughout the process. In A4S6, butyric acid production was observed only after 30 days of fermentation. From the perspective of metabolites, compared with sunflower ensiling alone, many bioactive substances such as flavonoids, alkaloids, and terpenes are upregulated in mixed ensiling.</p