Citacions bibliogràfiques segons el model de l'American Psychological Association

Guia bàsica per a fer les citacions bibliogràfiques segons el model APA (American Psychological Association), un estil de citació que s'aplica principalment en els àmbits de la comunicació, dret i psicologia

Profiling Energetics and Spectroscopic Signatures in Prototropic Tautomers of Asymmetric Phthalocyanine Analogues

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) were used to explain discrepancies in UV–vis and MCD spectra of the metal-free tribenzo­[<i>b</i>,<i>g</i>,<i>l</i>]­thiopheno­[<i>3</i>,<i>4</i>-<i>q</i>]­porphyrazine (<b>1</b>), substituted tribenzo­[<i>b</i>,<i>g</i>,<i>l</i>]­porphyrazine (<b>2</b>), and 2,3-bis­(methylcarboxyl)­phthalocyanine (<b>3</b>). On the basis of gas-phase and polarized continuum solvation model (PCM) DFT and TDDFT calculations, it was suggested that both NH tautomers contribute to the spectroscopic signature of <b>1</b>, whereas the Q-band region of <b>2</b> and <b>3</b> is dominated by a single NH tautomer. For all tested compounds, it was found that the combination of the BP86 exchange–correlation functional, 6-31G­(d) basis set, and TDDFT-PCM approach provides the best accuracy in energies of the Q_<i>x</i>- and Q_<i>y</i>-bands of the individual NH tautomers as well as correctly describes their relative energy differences, which are important in understanding of experimental spectroscopy of the target systems

Formation of an Unexpected Organometallic Mercury Compound in a Palladium-Catalyzed Reaction

The new and unexpected organometallic mercury compound <b>3</b> has been identified in the palladium-catalyzed reaction between bis­(ferrocenyl)mercury (<b>1</b>) and dimethylacetylenedicarboxylate (<b>2</b>) along with the expected dimethyl-(<i>Z</i>)-2,3-di­(ferrocenyl)-2-butenedioate (<b>4</b>) and biferrocene (<b>5</b>). Organometallic mercury complex <b>3</b> resulted from <i>syn</i>-addition of <b>1</b> to 2 equiv of <b>2</b>. Complex <b>3</b> has been characterized using NMR spectroscopy, while its structure was determined by X-ray crystallography. Complex <b>3</b> represents a rare example of an organomercury compound in which a mercury ion is coordinated to two vinylic fragments. Accurate, low-temperature experimental data for the crystal structure of <b>5</b> is also reported

Preparation and X‑ray Structural Study of 1‑Arylbenziodoxolones

Various 1-arylbenziodoxolones can be conveniently prepared from 2-iodobenzoic acid and arenes by a one-pot procedure using Oxone (2KHSO₅·KHSO₄·K₂SO₄) as an inexpensive and environmentally safe oxidant. This procedure is also applicable for the synthesis of the 7-methylbenziodoxolone ring system using 2-iodo-3-methylbenzoic acid as starting compound. Structures of four 1-arylbenziodoxolone derivatives were established by single-crystal X-ray diffraction analysis. An enhanced reactivity of 1-aryl-7-methylbenziodoxolones toward nucleophiles compared to unsubstituted 1-arylbenziodoxolones has been found

Synthesis, Characterization, and Electron-Transfer Processes in Indium Ferrocenyl-Containing Porphyrins and Their Fullerene Adducts

Three new indium­(III) tetra- and penta­(ferrocenyl)-substituted porphyrins of the general formula XInTFcP [X = Cl^–, OH^–, or Fc^–; TFcP = 5,10,15,20-tetraferrocenylporphyrin­(2-); Fc = ferrocene] have been prepared and characterized by UV–vis, magnetic circular dichroism (MCD), ¹H, ¹³C, 2D, and variable-temperature NMR spectroscopy, as well as elemental analysis. Molecular structures of the ClInTFcP, FcInTFcP, and FcInTFcP@4C₆₀ complexes were determined by X-ray crystallography with the last compound being not only the first example of a C₆₀ adduct to the organometallic porphyrins but also the first structure in which organometallic porphyrin antennas intercalated into four electron-transfer channels. The electronic structures and relative energies of individual atropisomers, as well as prospective electron-transfer properties of fullerene adducts of XInTFcP complexes, were investigated by the Density Functional Theory (DFT) approach. Redox properties of XInTFcP complexes were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in low-polarity solvent using noncoordinating electrolyte were crucial for the sequential oxidation of ferrocene substituents in XInTFcP compounds. In agreement with DFT calculations, the axial ferrocene ligand in FcInTFcP, with direct In–C σ-bond has a 240 mV lower oxidation potential compared to the first oxidation potential for equatorial ferrocene substituents connected to the porphyrin core. The first equatorial ferrocene oxidation process in all XInTFcP complexes is separated by at least 150 mV from the next three ferrocene based oxidations. The second, third, and fourth redox processes in the ferrocene region are more closely spaced. The addition of the bulky axial ferrocene ligand results in significantly larger rotational barriers for equatorial ferrocene substituents in FcInTFcP compared to the other complexes and leads to better defined redox waves in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments. Mixed-valence compounds of the general formula [XInTFcP]^<i>n</i>+ (<i>n</i> = 1, 2) were observed and characterized by spectroelectrochemical and chemical oxidation approaches. In all cases, the presence of the intense intervalence charge transfer (IVCT) bands associated with the oxidation of a single equatorial ferrocene substituent were detected in the NIR region confirming the presence of the iron-based mixed-valence species and suggesting long-range metal–metal coupling in the target systems. The resulting data from the mixed-valence [XInTFcP]^<i>n</i>+ (<i>n</i> = 1, 2) complexes matched very closely to the previously reported MTFcP and metal-free poly­(ferrocenyl)­porphyrins and were assigned as Robin and Day Class II mixed-valence compounds

Magnetic Circular Dichroism Spectroscopy of <i>N-</i>Confused Porphyrin and Its Ionized Forms

<i>N-</i>Confused porphyrin (NCP) and its externally methylated variant (MeNCP) were investigated using UV–vis and magnetic circular dichrosim (MCD) spectroscopies. In addition to evaluating the spectroscopy of the neutral compounds, the acid/base chemistry of these macrocycles was examined by the same methods. NCP exhibits two tautomeric states depending on the polarity of the solvent, and their protonation/deprotonation chemistries also differ depending on solvent polarity. DFT and TDDFT calculations were employed to evaluate the observed spectroscopic changes. Using both experimental and calculated results, we were able to determine the sites of protonation/deprotonation for both tautomeric forms of NCP. Inspection of the MCD Faraday B terms for all of the macrocycles presented in this report showed that the ΔHOMO > ΔLUMO condition is maintained in all cases, and these observations were in good agreement with the DFT calculations

Synthesis, Characterization, and Electron-Transfer Processes in Indium Ferrocenyl-Containing Porphyrins and Their Fullerene Adducts

Three new indium­(III) tetra- and penta­(ferrocenyl)-substituted porphyrins of the general formula XInTFcP [X = Cl^–, OH^–, or Fc^–; TFcP = 5,10,15,20-tetraferrocenylporphyrin­(2-); Fc = ferrocene] have been prepared and characterized by UV–vis, magnetic circular dichroism (MCD), ¹H, ¹³C, 2D, and variable-temperature NMR spectroscopy, as well as elemental analysis. Molecular structures of the ClInTFcP, FcInTFcP, and FcInTFcP@4C₆₀ complexes were determined by X-ray crystallography with the last compound being not only the first example of a C₆₀ adduct to the organometallic porphyrins but also the first structure in which organometallic porphyrin antennas intercalated into four electron-transfer channels. The electronic structures and relative energies of individual atropisomers, as well as prospective electron-transfer properties of fullerene adducts of XInTFcP complexes, were investigated by the Density Functional Theory (DFT) approach. Redox properties of XInTFcP complexes were investigated using electrochemical (CV and DPV), spectroelectrochemical, and chemical oxidation approaches. Electrochemical experiments conducted in low-polarity solvent using noncoordinating electrolyte were crucial for the sequential oxidation of ferrocene substituents in XInTFcP compounds. In agreement with DFT calculations, the axial ferrocene ligand in FcInTFcP, with direct In–C σ-bond has a 240 mV lower oxidation potential compared to the first oxidation potential for equatorial ferrocene substituents connected to the porphyrin core. The first equatorial ferrocene oxidation process in all XInTFcP complexes is separated by at least 150 mV from the next three ferrocene based oxidations. The second, third, and fourth redox processes in the ferrocene region are more closely spaced. The addition of the bulky axial ferrocene ligand results in significantly larger rotational barriers for equatorial ferrocene substituents in FcInTFcP compared to the other complexes and leads to better defined redox waves in cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments. Mixed-valence compounds of the general formula [XInTFcP]^<i>n</i>+ (<i>n</i> = 1, 2) were observed and characterized by spectroelectrochemical and chemical oxidation approaches. In all cases, the presence of the intense intervalence charge transfer (IVCT) bands associated with the oxidation of a single equatorial ferrocene substituent were detected in the NIR region confirming the presence of the iron-based mixed-valence species and suggesting long-range metal–metal coupling in the target systems. The resulting data from the mixed-valence [XInTFcP]^<i>n</i>+ (<i>n</i> = 1, 2) complexes matched very closely to the previously reported MTFcP and metal-free poly­(ferrocenyl)­porphyrins and were assigned as Robin and Day Class II mixed-valence compounds

Preparation and X‑ray Structural Study of 1‑Arylbenziodoxolones

Various 1-arylbenziodoxolones can be conveniently prepared from 2-iodobenzoic acid and arenes by a one-pot procedure using Oxone (2KHSO₅·KHSO₄·K₂SO₄) as an inexpensive and environmentally safe oxidant. This procedure is also applicable for the synthesis of the 7-methylbenziodoxolone ring system using 2-iodo-3-methylbenzoic acid as starting compound. Structures of four 1-arylbenziodoxolone derivatives were established by single-crystal X-ray diffraction analysis. An enhanced reactivity of 1-aryl-7-methylbenziodoxolones toward nucleophiles compared to unsubstituted 1-arylbenziodoxolones has been found

Unexpected Formation of Chiral Pincer CNN Nickel Complexes with β‑Diketiminato Type Ligands via C–H Activation: Synthesis, Properties, Structures, and Computational Studies

Reaction of lithiated chiral, unsymmetric β-diketimine type ligands <b>HL</b>^{<b>2a</b>–<b>e</b>} containing oxazoline moiety (<b>HL</b>^{<b>2a</b>–<b>e</b>} = 2-(2′-R₁NH)-phenyl-4-R₂-oxazoline) with <i>trans</i>-NiCl­(Ph)­(PPh₃)₂ afforded a series of new chiral CNN pincer type nickel complexes (<b>3a</b>–<b>3e</b>) via an unexpected cyclometalation at benzylic or aryl C–H positions. Single crystal X-ray diffraction analysis established the pincer coordination mode and the strained conformation. Chirality, and in one case, racemization of the target nickel complexes were confirmed by circular dichroism (CD) spectroscopy. Electronic structure and band assignments in experimental UV–vis and CD spectra were discussed on the basis of Density Functional Theory (DFT) and time-dependent (TD) DFT calculations

Energy Transfer from Colloidal Quantum Dots to Near-Infrared-Absorbing Tetraazaporphyrins for Enhanced Light Harvesting

We investigate the mechanisms of energy transfer from CdSe quantum dots (QDs) to porphyrin derivatives as a potential antenna system with enhanced light-harvesting efficiency. Two ferrocenyl-containing tetraazaporphyrin derivatives, namely, magnesium 2(3),7(8),12(13),17(18)-tetraferrocenyl-5,10,15,20-tetraazaporphyrin (TAP^FcMg) and magnesium 2(3),7(8),­12(13),­17(18)-tetra­cyano-3(2),8(7),13(12),18(17)-tetraferrocenyl-5,10,15,20-tetraazaporphyrin (TAP^FcCNMg), are used as energy acceptors in this proposed antenna system along with size-dependent QDs as donors. Our approach includes Förster resonance energy transfer (FRET) calculations as well as photoluminescence (PL) intensity and lifetime quenching measurements. Our FRET calculations indicate that higher energy transfer efficiency can be achieved with smaller quantum dot size. However, PL intensity and lifetime measurements suggest that energy transfer efficiency in QD/tetraazaporphyrin complexes is regulated by a competing trap-assisted ultrafast quenching mechanism, which is more dominant with smaller QD size. Furthermore, it is found that the trap-assisted quenching process is more active in QD/TAP^FcMg than QD/TAP^FcCNMg complexes. As a result, high efficiency energy transfer can be achieved in the complexes combining large QDs and TAP^FcCNMg, where trap-assisted quenching mechanism is suppressed. Our study suggests that CdSe quantum dots can be promising energy transfer donors for NIR-absorbing tetraazaporphyrins to form antenna systems with enhanced light-harvesting efficiency