Infrared spectra of metal β-ketoenolates and related complexes

Acetylacetone Photolysis at 280 nm Studied by Velocity-Map Ion Imaging

The photolysis of acetylacetone (AcAc) has been studied using velocity-map ion imaging with pulsed nanosecond lasers. The enolone tautomer of AcAc (CH3C(O)CH═C(OH)CH3) was excited in the strong UV absorption band by UV pulses at 280 nm, preparing the S2(ππ*) state, and products were probed after a short time delay by single-photon VUV ionization at 118.2 nm. Two-color UV + VUV time-of-flight mass spectra show enhancement of fragments at m/z = 15, 42, 43, 58, and 85 at the lowest UV pulse energies and depletion of the parent ion at m/z = 100. Ion images of the five major fragments are all isotropic, indicating dissociation lifetimes that are long on the timescale of molecular rotation but shorter than the laser pulse duration (<6 ns). The m/z = 15 and 85 fragments have identical momentum distributions with moderate translational energy release, suggesting that they are formed as a neutral product pair and likely via a Norrish type I dissociation of the enolone to form CH3 + C(O)CH═C(OH)CH3 over a barrier on a triplet surface. The m/z = 43 fragment may be tentatively assigned to the alternative Norrish type I pathway that produces CH3CO + CH2C(O)CH3 on S0 following phototautomerization to the diketone, although alternative mechanisms involving dissociative ionization of a larger primary photoproduct cannot be conclusively ruled out. The m/z = 42 and 58 fragments are not momentum-matched and consequently are not formed as a neutral pair via a unimolecular dissociation pathway on S0. They also likely originate from the dissociative ionization of primary photofragments. RRKM calculations suggest that unimolecular dissociation pathways that lead to molecular products on S0 are generally slow, implying an upper-limit lifetime of <46 ns after excitation at 280 nm. Time-dependent measurements suggest that the observed photofragments likely do not arise from dissociative ionization of energized AcAc S0*.

Tin(II) Acetylacetonate as a New Type of Tin Compensator Additive for Tin-Based Perovskite Solar Cells

Tin (Sn)-based perovskite is one of the most promising candidates for lead (Pb)-free perovskite light-absorbing materials applied in solar cells. However, the intrinsic Sn vacancy (V_Sn) defects seriously hinder the device performance, making the reported maximum power efficiency (PCE) of Sn-based perovskite solar cells (PSCs) far behind those of Pb-based ones. During the study, SnF₂ has been demonstrated as an indispensable Sn compensator additive to improve the device performance. Considering that the default use of SnF₂ and the selection of a Sn compensator has also been limited to tin(II) halides, i.e., SnCl₂, SnBr₂, and SnI₂, the role and work mechanism of the Sn compensator have not yet been clarified clearly. Herein, a new type of Sn compensator, tin(II) acetylacetonate [Sn (acac)₂], is introduced into Sn-based PSCs. It is found that in addition to tin compensation, the organic ligand acac^- can coordinate with Sn²⁺ in the precursor solution and improve the crystallization process of perovskites. Consequently, the maximum PCE of formamidinium tin triiodide (FASnI₃) solar cells is enhanced from 3.88 to 7.27% using Sn (acac)₂ as the Sn compensator.

Nanosized copper(ii) oxide/silica for catalytic generation of nitric oxide from S-nitrosothiols

The findings of this study suggest that copper(ii) oxide–silica nanoparticles produce NO from the GSNO species at physiological conditions in situ and could be used for designing biomedical materials with NO generating activity.

A simple photoluminescent strategy for pH and amine vapors detection based on Eu(iii)-complex functionalized material

A simple luminescence sensing strategy has been designed for pH and amine vapors detection after loaded luminescent compound Eu(DBM)₃Phen (LMOF-1), Eu(DBM)₃BPY (LMOF-2) on portable matrices such as neutral silica plate and normal filter paper.

X-ray diffraction and vibrational spectroscopic study of trans-bis(acetylacetonato)-bis(4-methylpyridine)cobalt(III)

Trans-bis(acetylacetonato)-bis(4-methylpyridine)cobalt(III)hexafluorophosphate, [AMPC]PF6, was synthesized and characterized by X-ray diffraction and vibrational spectroscopy. The title compound C22H28N2O4Co crystallizes with Z=2 in space group P-1 (#2). The molecular structure and vibrational spectra of this compound were investigated by means of density functional theory (DFT) calculations and the results were compared with the experimental data. The measured IR bands were interpreted in terms of the calculated vibrational normal modes and compared with the tris(acetylacetonate)Co(III) (Co(acac)3) and 4-methylpyridine (4-Mepy) vibrational spectra. The scaled theoretical wavenumbers and the structural parameters were in excellent agreement with the experimental data.

Synthesis, characterization and insights into stable and well organized hexagonal mesoporous zinc-doped alumina as promising metathesis catalysts carrier

ZnCl₂-modified hexagonal mesoporous alumina was successfully synthesized, yielding Al–O–Zn–Cl species for supporting methyltrioxorhenium towards methyl oleate self-metathesis.

Strong metal-metal coupling in mixed-valent intermediates [Cl(L)Ru(μ-tppz)Ru(L)Cl]+, L = β-diketonato ligands, tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine

Five diruthenium(II) complexes [Cl(L)Ru(μ-tppz)Ru(L)Cl] (1-5) containing differently substituted β-diketonato derivatives (1: L = 2,4-pentanedionato; 2: L = 3,5-heptanedionato; 3: L = 2,2,6,6-tetramethyl-3,5-heptanedionato; 4: L = 3-methyl-2,4-pentanedionato; 5: L = 3-ethyl-2,4-pentanedionato) as ancillary ligands (L) were synthesized and studied by spectroelectrochemistry (UV-Vis-NIR, electron paramagnetic resonance (EPR)). X-ray structural characterisation revealed anti (1, 2, 5) or syn (3) configuration as well as non-planarity of the bis-tridentate tppz bridge and strong dπ(Ru(II)) → π*(pyrazine, tppz) back-bonding. The widely separated one-electron oxidation steps, Ru(II)Ru(II)/Ru(II)Ru(III) and Ru(II)Ru(III)/Ru(III)Ru(III), result in large comproportionation constants (K(c)) of ≥10(10) for the mixed-valent intermediates. The syn-configurated (n) exhibits a particularly high K(c) of 10(12) for n = 1+, accompanied by density functional theory (DFT)-calculated minimum Ru-N bond lengths for this Ru(II)Ru(III) intermediate. The electrogenerated mixed-valent states 1(+)-5(+) exhibit anisotropic EPR spectra at 110 K with average values <g> of 2.304-2.234 and g anisotropies Δg = g(1)-g(3) of 0.82-0.99. Metal-to-metal charge transfer (MMCT) absorptions occur for 1(+)-5(+) in the NIR region at 1660 nm-1750 nm (ε ≈ 2700 dm(3) mol(-1) cm(-1), Δν(1/2) ≈ 1800 cm(-1)). DFT calculations of 1(+) and 3(+) yield comparable Mulliken spin densities of about 0.60 for the metal ions, corresponding to valence-delocalised situations (Ru(2.5))(2). Rather large spin densities of about -0.4 were calculated for the tppz bridges in 1(+) and 3(+). The calculated electronic interaction values (V(AB)) for 1(+)-5(+) are about 3000 cm(-1), comparable to that for the Creutz-Taube ion at 3185 cm(-1). The DFT calculations predict that the Ru(III)Ru(III) forms in 1(2+)-5(2+) prefer a triplet (S = 1) ground state with ΔE (S = 0 - S = 1) ∼5000 cm(-1). One-electron reduction takes place at the tppz bridge which results in species [Cl(L)Ru(II)(μ-tppz˙(-))Ru(II)(L)Cl](-) (1˙(-)-3˙(-), 5˙(-)) which exhibit free radical-type EPR signals and NIR transitions typical of the tppz radical anion. The system 4(n) is distinguished by lability of the Ru-Cl bonds.

IR spectroscopic investigation of cis-(CH(3))(2)Au(O,O'-acac) and cis-(CD(3))(2)Au(O,O'-acac)

The IR spectrum of cis-(CH(3))(2)Au(O,O'-acac) has been reassigned by comparing frequencies for cis-(CH(3))(2)Au(O,O'-acac) and cis-(CD(3))(2)Au(O,O'-acac), and by analysis of the DFT-calculated normal modes and their frequencies for the isolated molecules. The vibrational intensity in the C-H stretching region arises almost entirely from the cis-(CH(3))(2)Au fragment, while the methyl deformation intensity is largely of acetylacetonato ligand origin. A low frequency mode in the C-H stretching region is the first overtone of the delta(a)(CH(3)) mode of cis-(CH(3))(2)Au. The Au-C stretching modes are affected by deuteration of the cis-(CH(3))(2)Au fragment, while the Au-O stretching modes are not.

Facile synthesis for ordered mesoporous gamma-aluminas with high thermal stability

The facile synthesis of highly ordered mesoporous aluminas with high thermal stability and tunable pore sizes is systematically investigated. The general synthesis strategy is based on a sol-gel process associated with nonionic block copolymer as templates in ethanol solvent. Small-angle XRD, TEM, and nitrogen adsorption and desorption results show that these mesoporous aluminas possess a highly ordered 2D hexagonal mesostructure, which is resistant to high temperature up to 1000 degrees C. Ordered mesoporous structures with tunable pore sizes are obtained with various precursors, different acids as pH adjustors, and different block copolymers as templates. These mesoporous aluminas have large surface areas (ca. 400 m2/g), pore volumes (ca. 0.70 cm3/g), and narrow pore-size distributions. The influence of the complexation ability of anions and hydro-carboxylic acid, acid volatility, and other important synthesis conditions are discussed in detail. Utilizing this simple strategy, we also obtained partly ordered mesoporous alumina with hydrous aluminum nitrate as the precursor. FTIR pyridine adsorption measurements indicate that a large amount of Lewis acid sites exist in these mesoporous aluminas. These materials are expected to be good candidates in catalysis due to the uniform pore structures, large surface areas, tunable pore sizes, and large amounts of surface Lewis acid sites. Loaded with ruthenium, the representative mesoporous alumina exhibits reactant size selectivity in hydrogenation of acetone, D-glucose, and D-(+)-cellobiose as a test reaction, indicating the potential applications in shape-selective catalysis.

Effects of Central Metal Ions on Vibrational Circular Dichroism Spectra of Tris-(β-diketonato)metal(III) Complexes

Vibrational circular dichroism (VCD) spectra of a series of [M(III)(acac)3] (acac = acetylacetonato; M = Cr, Co, Ru, Rh, Ir, and Al) and [M(III)(acac)2(dbm)] (dbm = dibenzoylmethanato; M = Cr, Co, and Ru) have been investigated experimentally and/or theoretically in order to see the effect of the central metal ion on the vibrational dynamics of ligands. The optical antipodes give the mirror-imaged spectra in the region of 1700-1000 cm(-1). The remarkable effect of the central metal ion is observed experimentally on the VCD peaks due to C-O stretches (1500-1300 cm(-1)) for both [M(III)(acac)3] and [M(III)(acac)2(dbm)]. In the case of Delta-[M(III)(acac)3], for example, the order of frequency of two C-O stretches (E and A2 symmetries) is dependent on the kind of a central metal ion as follows: E (-) > A2 (+) for M = Co, Rh, and Ir, while A2 (+) > E (-) for M = Cr and Ru. In the case of Delta-[M(III)(acac)2(dbm)], the order of frequency of three C-O stretches (A, B, and B symmetries) is as follows: A (-) > B (+) > B (+) for Co(III), B (+) > A (-) > B (-) for Cr(III), and A (-) > B (+) > B (-) for Ru(III). These results imply that the energy levels of C-O stretches are delicately affected by the kind of central metal ion. Since such detailed information is not obtained from the IR spectra alone, the VCD spectrum can probe the effect of the central metal ion on interligand cooperative vibration modes.

Crystal structure of lead(ii) acetylacetonate and the structure of the acetylacetone solvated lead(ii) ion in solution studied by large-angle X-ray scattering

The crystal structure of bis(acetylacetonato)lead(II) and the structure of the acetylacetone solvated lead(II) ion in solution have been determined by single-crystal X-ray diffraction and large-angle X-ray scattering (LAXS), respectively. The acetylacetone is deprotonated and acts as a bidentate anionic ligand (acac-) in the solid Pb(acac)2 compound. The lead(II) ion binds four oxygen atoms strongly in a nearly flat pyramidal configuration with Pb-O bond lengths in the range 2.32-2.37 A, and additionally three oxygens from neighboring complexes at 3.01-3.26 A. Acetylacetone acts as a solvent (Hacac) at dissolution of lead(II) trifluoromethanesulfonate forming a pentasolvate with a mean Pb-O bond distance of 2.724(5) A. The 6s2 lone electron pair on the lead(II) ion becomes stereochemically active in the crystalline acetylacetonate complex, while it is inactive in the solvate in solution. The solution was also analysed using IR and 1H NMR spectroscopy.

Density functional theory study of the Fourier transform infrared and Raman spectra of Cu(II) bis-acetylacetone

Fourier transform infrared and Fourier transform Raman spectra of Cu(II) bis-acetylacetone have been obtained. The geometry, frequency and intensity of the vibrational bands of this compound and its 1,5-(13)C(2), 3-(13)C, 1,3,5-(13)C(3), 2,4-(13)C(2), (18)O(2) and 2,4-(13)C(2)-(18)O(2) derivatives were obtained by the density functional theory (DFT) with the B3LYP functional and using the 6-31G(*) and 3-21G(*) basis sets. The calculated frequencies are compared with the solid infrared and Raman spectra. All the measured infrared and Raman bands were interpreted in terms of the calculated vibrational modes. The percentage of deviation of the bond lengths and bond angles gives a good picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated geometrical parameters show slight differences compared with the experimental results. These differences can be explained by the different physical state of Cu(II) bis-acetylacetone. The DFT-B3LYP calculations assumed a free molecule in the gas phase. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes.

Development of novel pillared clays for the encapsulation of inorganic complexes

Several pillared clays were prepared by using a polyalcohol (ethylene glycol or poly(vinyl alcohol)) or a poly(ethylene oxide) surfactant as an interlayer gallery template and an aluminum oligomer species as the pillaring agent. The use of polyalcohols or nonionic surfactants, such as Tergitol, gave materials which, in general, presented larger basal spacing than those found for the solids prepared by a similar procedure but without additives. The initial positive effect in the expansion of the clay interlayers was not totally retained after calcination of the materials; most probably, at the end, the basal spacing is still ruled by the intercalating aluminum species. The pillared clay with the largest basal spacing and specific surface area was used to encapsulate copper(II) complexes with pentadentate N3O2 Schiff base ligands derived from copper(II) acetylacetonate by in situ synthesis. The characterization made (X-ray diffraction, X-ray photoelectron spectroscopy, FTIR spectroscopy, chemical analysis, and low-temperature N2 adsorption) provided evidence that copper(II) complexes with pentadentate N3O2 Schiff base ligands were efficiently entrapped within the lower dimension pores of the pillared clay and that they interact strongly with the pillared clay matrix.

Vibrational assignment of aluminum(III) tris-acetylacetone

The geometry, frequency and intensity of the vibrational bands of aluminum(III) Tris-acetylacetone Al(AA)3 and its 1,3,5-(13)C derivative were obtained by the Hartree-Fock (HF) and Density Functional Theory (DFT) with the B3LYP, B1LYP, and G96LYP functionals and using the 6-31G* basis set. The calculated frequencies are compared with the solid IR and Raman spectra. All of the measured IR and Raman bands were interpreted in terms of the calculated vibrational modes. Most computed bands are predicted to be at higher wavenumbers than the experimental bands. The calculated bond lengths and bond angles are in good agreement with the experimental results. Analysis of the vibrational spectra indicates a strong coupling between the chelated ring modes. Four bands in the 500-390 cm(-1) frequency range are assigned to the vibrations of metal-ligand bonds.

Vibrational assignment of 4-amino-3-penten-2-one

The infrared and Raman spectra of 4-amino-3-penten-2-one and its two deuterated analogous have been measured. Comparison between the spectra recorded with two techniques, density functional theory (DFT) calculations and the spectral behavior upon deuteration was used for assignment of the vibrational spectra of the titled compound. DFT suggests a relatively strong intramolecular bent hydrogen bond with N...O distance in the range of 2.64-2.67 A, which is in agreement with the observed vNH at 3180 cm(-1). Existence of an intermolecular hydrogen bond is also shown in both solid and solution phases. The spectroscopic data support the enamine structure for this compound rather than imine structure.

Density functional theory study of the fourier transform infrared and Raman spectra of dichloro-bis(2,4-pentanedionate)tin(IV)

Fourier transform infrared and Fourier transform Raman spectra of dichloro-bis(2,4-pentanedionate)tin(IV) have been obtained. Density functional theory (DFT) BLYP calculations, have been carried out with the purpose of understanding the metal-ligand region spectra of this compound. Vibrational wavenumbers calculated by BLYP/6-31G* force fields are closed with the experimental results. The percentage of deviation of the bond lengths and bond angles gives a good picture of the normal modes, and serves as a basis for the assignment of the wavenumbers. The calculated geometrical parameters show slight differences compared with the experimental ones, and these differences can be explained by the different physical state of Sn(acac)2Cl2. The DFT-BLYP calculations assumed a free molecule in the gas phase. The experimental wavenumbers are obtained from the spectra of solid samples.

Synthesis of beta-Imino Carbonyl Enolato Complexes by Reaction of Nickel(II), Palladium(II), and Copper(II) Acetates with the Enaminodiones (MeOCO)(RCO)CC(R')NH(2) (R = Me, OMe; R' = Et, EtOCO)

Nickel(II), palladium(II), and copper(II) acetates undertake exchange reaction with the beta-enaminodiones (MeOCO)(RCO)CC(R')NH(2) (R = Me, OMe; R' = Et, EtOCO) in ethanol to give the neutral complexes [M((MeOCO)(RCO)CC(R')NH)(2)] (1-8) [R = Me, R' = Et: M = Ni (1), Pd (2a,b), Cu (3); R = Me, R' = EtOCO: M = Ni (4), Pd (5), Cu (6); R = MeO, R' = Et, M = Pd (7a,b); R = MeO, R' = EtOCO, M = Pd (8a,b)]. The trifunctional N,O,O ligands act in all cases as bidentate through the imino and one carbonyl group. Complexes 1-8 are all monomers with a square planar geometry. Nickel and palladium complexes show more than one form in the solid state. For example the palladium complex 2 has been synthesized in two forms a and b, which differ in the conformation of the methoxy carbonyl substituent of the chelate ring, while the third isomer or conformer is obtained by thermal treatment at 120 degrees C. Complexes 7 and 8 also exhibit two forms which differ in the degree of intermolecular hydrogen bonding. Both 7b and 8b crystallize in monoclinic unit cells [7b: space group P2(1)/n, a = 11.963(2), b = 8.438(1), c = 19.637(2) Å, beta = 94.2(1) degrees. 8b: P2(1)/c, a = 10.698(2), b = 14.902(2), c = 13.918(2) Å, beta = 95.2(1) degrees ] containing four molecules linked by intermolecular hydrogen bonding [N-H.O=C, 2.14-2.36 Å]. All complexes are thermally stable and volatile. Their mass spectra exhibit intense molecular ion peaks under EI mass conditions.

Syntheses, Structures, and Thermal Behavior of Cu(hfacac) Complexes Derived from Ethanolamines

A series of novel precursors for MOCVD of metallic copper have been synthesized and structurally characterized. These precursors are composed of Cu(hfacac)(2), which serves as a volatile source of Cu, and amino alcohols, which act as reductants and anchor firmly to the copper center through the amine unit. In some cases, a proton transfer from the coordinated alcohol to the hfacac ligand results in the formation of an alkoxide unit and the release of the free Hhfacac. Metallic copper films can be deposited by MOCVD at 300 degrees C without any external reductant. Crystal data: Cu(hfacac)(2).C(7)H(8) (-103 degrees C), a = 6.510(6) Å, b = 8.594(7) Å, c = 18.478(15) Å, orthorhombic space group Pmnn, Z = 2; Cu(hfacac)(2)(H(2)NCH(2)CH(2)OH) (-158 degrees C), a = 13.145(1) Å, b = 13.418(1) Å, c = 11.245(1) Å, alpha = 110.39(1) degrees, beta = 99.12(1) degrees, gamma = 97.90(1) degrees, triclinic space group P&onemacr;, Z = 4; [Cu(hfacac)(Me(2)NCH(2)CH(2)O)](2) (-153 degrees C), a = 9.259(2) Å, b = 12.011(3) Å, c = 6.304(1) Å, alpha = 91.19(1) degrees, beta = 106.66(1) degrees, gamma = 74.83(1) degrees, triclinic space group P&onemacr;, Z = 1; Cu(hfacac)[N(CH(2)CH(2)OH)(2)(CH(2)CH(2)O)].MeOH (-168 degrees C), a = 10.075(4) Å, b = 8.611(4) Å, c = 19.259(9) Å, beta = 99.82(2) degrees, monoclinic space group P2(1)/m, Z = 4.

Variable Coordination and Conformation of the 3-Cyano-2,4-pentanedionato Anion in a Mixed-Ligand Binuclear Copper(II) Chelate

The addition of dipyridylamine to bis(3-cyano-2,4-pentanedionato)copper(II), Cu(NC-acac)(2), induces changes in the mode of interaction and the conformation of the NC-acac(-) anion. The structure of the resulting binuclear compound was determined from a single microcrystal (monoclinic, space group P2(1), a = 7.894(7) Å, b = 25.550(24) Å, c = 11.661(13) Å, beta = 106.10(8) degrees, Z = 2, R(1) = 0.0564, (w)R(2) = 0.1197). In the addition compound {[Cu(NC-acac)dipyamH](NC-acac)}(2) when the NC-acac(-) acts as a chelating and bridging ligand, it assumes the commonly observed U(Z,Z) conformation, while behavior as weakly N-coordinated unidentate counteranion imposes the rarely encountered S(Z,E) conformation. In the [Cu(NC-acac)dipyamH](NC-acac)] entities one of the copper(II) centers is a 4 + 2 Jahn-Teller complex while the other is a square-based pyramid.