Electrochemical and Spectroelectrochemical Analysis of 4‐(4‐(5‐Phenyl‐1,3,4‐oxadiazole‐2‐yl)phenoxy)‐Substituted Cobalt(II), Lead(II) and Metal‐Free Phthalocyanines

Electrochemical and spectroelectrochemical analyses of 4‐(4‐(5‐phenyl‐1,3,4‐oxadiazole‐2‐yl)phenoxy)‐substituted metal‐free phthalocyanine ( H₂Pc ( 1 )) and metallated phthalocyanines ( PbPc ( 2 ) and CoPc ( 3 )) were performed in solution. Voltammetric characterizations of the phthalocyanine complexes were investigated by using cyclic voltammetry and square wave voltammetry techniques. CoPc ( 3 ) gave common metal and ring based electron transfer reactions; however they split due to the aggregation. Although PbPc ( 2 ) illustrated reversible reduction processes during the voltammetric measurements, it was de‐metallized and thus turned to the metal free phthalocyanine during repetitive voltammetric cycles and in situ spectroelectrochemical measurements.     

Methyloxy Substituted Heteroleptic Bis(phthalocyaninato) Yttrium Complexes: Density Functional Calculations

The effects of alkyloxy substituents attached to one phthalocyanine ligand of three heteroleptic bis(phthalocyaninato) yttrium complexes Y(Pc)[Pc(α‐OCH₃)₄] ( 1 ), Y(Pc)[Pc(α‐OCH₃)₈] ( 2 ), and Y(Pc)[Pc(β‐OCH₃)₈] ( 3 ), as well as their reduction products {Y(Pc)[Pc(α‐OCH₃)₄]}^? ( 4 ), {Y(Pc)[Pc(α‐OCH₃)₈]}^? ( 5 ), and {Y(Pc)[Pc(β‐OCH₃)₈]}^? ( 6 ) [H₂Pc(α‐OCH₃)₄=1,8,15,22‐tetrakis(methyloxy)phthalocyanine; H₂Pc(α‐OCH₃)₈=1,4,8,11,15,18,22,25‐octakis(methyloxy)phthalocyanine; H₂Pc(β‐OCH₃)₈=2,3,9,10,16,17,23,24‐octakis(methyloxy)phthalocyanine] are studied by DFT calculations. Good consistency is found between the calculated results and experimental data for the electronic absorption, IR, and Raman spectra of 1 and 3 . Introduction of electron‐donating methyloxy groups on one phthalocyanine ring of the heteroleptic double‐deckers induces structural deformation in both phthalocyanine ligands, electron transfer between the two phthalocyanine rings, changes in orbital energy and composition, shift of electronic absorption bands, and different vibrational modes of the unsubstituted and substituted phthalocyanine ligands in the IR and Raman spectra in comparison with the unsubstituted homoleptic counterpart Y(Pc)₂. The calculations reveal that incorporation of methyloxy substituents at the nonperipheral positions has greater influence on the structure and spectroscopic properties of bis(phthalocyaninato) yttrium double‐deckers than at the peripheral positions, which increases with increasing number of substituents. Nevertheless, the substituent effect of alkyloxy substituents at one phthalocyanine ligand of the double‐decker on the unsubstituted phthalocyanine ring and on the whole molecule and the importance of the position and number of alkyloxy substituents are discussed. In addition, the effect of reducing 1 – 3 to 4 – 6 on the structure and spectroscopic properties of the bis(phthalocyaninato) yttrium compounds is also discussed. This systemic DFT study is not only useful for understanding the structure and spectroscopic properties of bis(phthalocyaninato) rare earth metal complexes but also helpful in designing and preparing double‐deckers with tunable structure and properties.     

The development of highly selective approaches to sandwich-type heteroleptic double- and triple-decker lutetium(III) and europium(III) phthalocyanine complexes

The selective synthesis of heteroleptic (heteronuclear) sandwich-type lanthanide phthalocyanines has been accomplished. Double-decker complexes ^BuPcLnPc, and ^BuPcLnPc^Cl (Ln = Lu, Eu; ^BuPc = 2,3,9,10,16,17,23,24-octabutylphthalocyaninate; Pc = phthalocyaninate, ^ClPc = 2,3,9,10,16,17,23,24-octachlorophthalocyaninate) were obtained in good yields by a direct interaction of metal-free ligand ^BuPcH₂ with the monophthalocyanines PcLnOAc or ^ClPcLnOAc. Heteronuclear triple-decker phthalocyanines PcEu^RPcLu^RPc, ^ClPcEu^RPcLu^RPc and ^BuPcEu^RPcLu^RPc (^RPc = ^BuPc, ^tBuPc; ^tBuPc = 2(3),9(10),16(17),23(24)-tetra-tert-butylphthalocyaninate) were obtained from the corresponding mono-(PcEuOAc, ^ClPcEuOAc, ^BuPcEuOAc) and bisphthalocyanines (^RPc₂Lu) under similar conditions.     

Noble‐Metal‐Free Photocatalytic H2 Generation: Active and Inactive ‘Black’ TiO2 Nanotubes and Synergistic Effects

Over the past five years a number of different synthesis approaches has been reported to obtain so‐called ‘black’ titania. One of the outstanding features of the material is that certain synthesis processes lead to the formation of an intrinsic co‐catalytic center and thus enable noble‐metal free photocatalytic H₂‐generation. In the present work, using TiO₂ nanotube layers, we compare three common ‘blackening’ approaches, namely i) the original high‐pressure hydrogenation (HPT‐H₂), ii) a classic high temperature reduction in Ar, and iii) an electrochemical (cathodic) reduction. We demonstrate that except for high pressure hydrogenation also cathodic reduction leads to an activation of TiO₂ ‐ that is, it exhibits noble‐metal‐free photocatalytic H₂ generation. Moreover, we show that a combination of cathodic reduction/high pressure hydrogenation leads to a synergistic effect, that is, a significant enhancement of the combined co‐catalytic activity.     

Tetrakis‐phthalocyanines bearing electron‐withdrawing fluoro functionality: Synthesis,spectroscopy, and electrochemistry

In this study, 2,9,16,23‐tetrakis‐4′‐(2,3,5,6‐tetrafluoro)‐phenoxy‐phthalocyaninatometalfree and metal(II) complexes, (H₂PcBzF₁₆, ZnPcOBzF₁₆, CuPcOBzF₁₆, and CoPcOBzF₁₆) (Bz: Benzene) (2H, Zn, Cu, and Co), have been prepared directly from the corresponding 4′‐(2,3,5,6‐fluorophenylthio)‐phthalonitrile compounds in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in high boiling quinoline solvent. Tetrafluoro atoms on 2,3,5,6‐position of benzene at the peripheral sites of phthalocyanines (Pcs) give rise interesting solubility to tetrakismetallophthalocyanines. Although all complexes were soluble in DCM, CHCl₃, THF, DMF, and DMSO with increasing order, complexes synthesized, particularly H₂PcBzF₁₆, CuPcOBzF₁₆, have very limited solubility in DMF and DMSO. The complexes have been characterized by elemental analysis, FTIR, ¹H NMR, UV–vis, and MALDI–TOF mass spectral data. The cyclic voltammetry and differential pulsed voltammetry of the complexes show that while H₂PcBzF₁₆, CuPcOBzF₁₆, and ZnPcOBzF₁₆ give ligand‐based reduction and oxidation processes, CoPcOBzF₁₆ gives both ligand and metal‐based redox processes, in harmony with the common metallophthalocyanine complexes. Redox processes due to both aggregated and disaggregated species were simultaneously observed during the first reduction process. The nature of the metal‐based redox processes was confirmed using spectroelectrochemical measurements. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:262–271, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20545     

Siamese‐Twin Porphyrin: A Pyrazole‐Based Expanded Porphyrin of Persistent Helical Conformation

The 3+3‐type synthesis of a pyrazole‐based expanded porphyrin 22 H₄ , a hexaphyrin analogue named Siamese‐twin porphyrin, and its homobimetallic diamagnetic nickel(II) and paramagnetic copper(II) complexes, 22 Ni₂ and 22 Cu₂ , are described. The structure of the macrocycle composed of four pyrroles and two pyrazoles all linked by single carbon atoms, can be interpreted as two conjoined porphyrin‐like subunits, with the two opposing pyrazoles acting as the fusion points. Variable‐temperature 1D and 2D NMR spectroscopic analyses suggested a conformationally flexible structure for 22 H₄ . NMR and UV/Vis spectroscopic evidence as well as structural parameters proved the macrocycle to be non‐aromatic, though each half of the molecule is fully conjugated. UV/Vis and NMR spectroscopic titrations of the free base macrocycle with acid showed it to be dibasic. In the complexes, each metal ion is coordinated in a square‐planar fashion by a dianionic, porphyrin‐like {N₄} binding pocket. The solid‐state structures of the dication and both metal complexes were elucidated by single‐crystal diffractometry. The conformations of the three structures are all similar to each other and strongly twisted, rendering the molecules chiral. The persistent helical twist in the protonated form of the free base and in both metal complexes permitted resolution of these enantiomeric helimers by HPLC on a chiral phase. The absolute stereostructures of 22 H₆ ²⁺, 22 Ni₂ , and 22 Cu₂ were assigned by a combination of experimental electronic circular dichroism (ECD) investigations and quantum‐chemical ECD calculations. The synthesis of the first member of this long‐sought class of expanded porphyrin‐like macrocycles lays the foundation for the study of the interactions of the metal centers within their bimetallic complexes.     

Lanthanide(III) Bis(phthalocyaninato)–[60]Fullerene Dyads: Synthesis,Characterization, and Photophysical Properties

A novel series of double‐decker lanthanide(III) bis(phthalocyaninato)–C₆₀ dyads [Ln^III(Pc)(Pc′)]–C₆₀ (M=Sm, Eu, Lu; Pc=phthalocyanine) ( 1 a – c ) have been synthesized from unsymmetrically functionalized heteroleptic sandwich complexes [Ln^III(Pc)(Pc′)] (Ln=Sm, Eu, Lu) 3 a – c and fulleropyrrolidine carboxylic acid 2 . The sandwich complexes 3 a – c were obtained by means of a stepwise procedure from unsymmetrically substituted free‐base phthalocyanine 5 , which was first transformed into the monophthalocyaninato intermediate [Ln^III(acac)(Pc)] and further reacted with 1,2‐dicyanobenzene in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU). ¹H NMR spectra of the bis(phthalocyaninato) complexes 3 a – c and dyads 1 a – c were obtained by adding hydrazine hydrate to solutions of the complexes in [D₇]DMF, a treatment that converts the free radical double‐deckers into the protonated species, that is, [Ln^III(Pc)(Pc′)H] and [Ln^III(Pc)(Pc′)H]–C₆₀. The electronic absorption spectra of 3 a – c and 1 a – c in THF exhibit typical transitions of free‐radical sandwich complexes. In the case of dyads 1 a – c , the spectra display the absorption bands of both constituents, but no evidence of ground‐state interactions could be appreciated. When the UV/Vis spectra of 3 a – c and 1 a – c were recorded in DMF, typical features of the reduced forms were observed. Cyclic voltammetry studies for 3 a – c and 1 a – c were performed in THF. The electrochemical behavior of dyads 1 a – c is almost the exact sum of the behavior of the components, namely the double‐decker [Ln^III(Pc)(Pc′)] and the C₆₀ fullerene, thus confirming the lack of ground‐state interactions between the electroactive units. Photophysical studies on dyads 1 a – c indicate that only after irradiation at 387 nm, which excites both C₆₀ and [Ln^III(Pc)(Pc′)] components, a photoinduced electron transfer from the [Ln^III(Pc)(Pc′)] to C₆₀ occurs.     

Faujasite-type zeolites modified with iron perfluorophthalocyanines: Synthesis and characterization

The synthesis and characterization of hexadeca- or perfluorophthalocyanine complexes of iron(II) (FeF₁₆Pc) in synthetic faujasite-type zeolites is reported. The encapsulation of FeF₁₆Pc in NaY zeolite by the template synthesis method as well as the synthesis of NaX around FeF₁₆Pc are discussed. A spectroscopic (UV—VIS, IR) and electrochemical analysis of the modified zeolites, providing evidence for encapsulation, is presented and compared with the unsubstituted FePc complex.     

Synthesis,Structures, and Properties of Crystalline Salts with Radical Anions of Metal‐Containing and Metal‐Free Phthalocyanines

Radical anion salts of metal‐containing and metal‐free phthalocyanines [MPc(3?)]^.?, where M=Cu^II, Ni^II, H₂, Sn^II, Pb^II, Ti^IVO, and V^IVO ( 1 – 10 ) with tetraalkylammonium cations have been obtained as single crystals by phthalocyanine reduction with sodium fluorenone ketyl. Their formation is accompanied by the Pc ligand reduction and affects the molecular structure of metal phthalocyanine radical anions as well as their optical and magnetic properties. Radical anions are characterized by the alternation of short and long C?N_imine bonds in the Pc ligand owing to the disruption of its aromaticity. Salts 1 – 10 show new bands at 833–1041 nm in the NIR range, whereas the Q‐ and Soret bands are blue‐shifted by 0.13–0.25 eV (38‐92 nm) and 0.04–0.07 eV (4–13 nm), respectively. Radical anions with Ni^II, Sn^II, Pb^II, and Ti^IVO have S=1/2 spin state, whereas [Cu^IIPc(3?)]^.? and [V^IVOPc(3?)]^.? containing paramagnetic Cu^II and V^IVO have two S=1/2 spins per radical anion. Central metal atoms strongly affect EPR spectra of phthalocyanine radical anions. Instead of narrow EPR signals characteristic of metal‐free phthalocyanine radical anions [H₂Pc(3?)]^.? (linewidth of 0.08–0.24 mT), broad EPR signals are manifested (linewidth of 2–70 mT) with g‐factors and linewidths that are strongly temperature‐dependent. Salt 11 containing the [Na^IPc(2?)]^? anions as well as previously studied [Fe^IPc(2?)]^? and [Co^IPc(2?)]^? anions that are formed without reduction of the Pc ligand do not show changes in molecular structure or optical and magnetic properties characteristic of [MPc(3?)]^.? in 1 – 10 .     

Chemistry of Diruthenium and Dirhodium Analogues of Pentaborane(9): Synthesis and Characterization of Metal N,S‐Heterocyclic Carbene and B‐Agostic Complexes

Building upon our earlier results on the synthesis of electron‐precise transition‐metal–boron complexes, we continue to investigate the reactivity of pentaborane(9) and tetraborane(10) analogues of ruthenium and rhodium towards thiazolyl and oxazolyl ligands. Thus, mild thermolysis of nido‐[(Cp*RuH)₂B₃H₇] ( 1 ) with 2‐mercaptobenzothiazole (2‐mbtz) and 2‐mercaptobenzoxazole (2‐mboz) led to the isolation of Cp*‐based (Cp*=η⁵‐C₅Me₅) borate complexes 5 a , b [Cp*RuBH₃L] ( 5 a : L=C₇H₄NS₂; 5 b : L=C₇H₄NOS)) and agostic complexes 7 a , b [Cp*RuBH₂(L)₂], ( 7 a : L=C₇H₄NS₂; 7 b : L=C₇H₄NOS). In a similar fashion, a rhodium analogue of pentaborane(9), nido‐[(Cp*Rh)₂B₃H₇] ( 2 ) yielded rhodaboratrane [Cp*RhBH(L)₂], 10 (L=C₇H₄NS₂). Interestingly, when the reaction was performed with an excess of 2‐mbtz, it led to the formation of the first structurally characterized N,S‐heterocyclic rhodium‐carbene complex [(Cp*Rh)(L₂)(1‐benzothiazol‐2‐ylidene)] ( 11 ) (L=C₇H₄NS₂). Furthermore, to evaluate the scope of this new route, we extended this chemistry towards the diruthenium analogue of tetraborane(10), arachno‐[(Cp*RuCO)₂B₂H₆] ( 3 ), in which the metal center possesses different ancillary ligands.     

Photochemically Induced Reductive Elimination as a Route to a Zirconocene Complex with a Strongly Activated N2 Ligand

The zirconocene dinitrogen complex [{(η⁵‐C₅Me₄H)₂Zr}₂(μ₂,η²,η²‐N₂)] was synthesized by photochemical reductive elimination from the corresponding zirconium bis(aryl) or aryl hydride complexes, providing a high‐yielding, alkali metal‐free route to strongly activated early‐metal N₂ complexes. Mechanistic studies support the intermediacy of zirconocene arene complexes that in the absence of sufficient dinitrogen promote C? H activation or undergo comproportion to formally Zr^III complexes. When N₂ is in excess arene displacement gives rise to strong dinitrogen activation.     

Broad Hexagonal Columnar Mesophases Formation in Bioinspired Transition‐Metal Complexes of Simple Fatty Acid meta‐Octaester Derivatives of meso‐Tetraphenyl Porphyrins

A series of meta‐substituted fatty acid octaester derivatives and their transition‐metal complexes of meso‐ tetraphenyl porphyrins (TPP‐8OOCR, with R=C_n?1H_2n?1, n=8, 12, or 16) have been prepared through very simple synthesis protocols. The thermotropic phase behavior and the liquid crystalline (LC) organization structures of the synthesized porphyrin derivatives were systematically investigated by a combination of differential scanning calorimetry (DSC), polarized optical microscopy (POM), and variable‐temperature small‐angle X‐ray scattering/wide‐angle X‐ray scattering (SAXS/WAXS) techniques. The shorter octanoic acid ester substituted porphyrin (C8‐TPP) did not show liquid crystallinity and its metal porphyrins exhibited an uncommon columnar mesophase. The lauric acid octaester (C12‐TPP) and the palmitic acid octaester (C16‐TPP) series porphyrins generated hexagonal columnar mesophase Col_h. Moreover, the metal porphyrins C12‐TPPM and C16‐TPPM with M=Zn, Cu, or Ni, exhibited well‐organized Col_h mesophases of broad LC temperature ranges increasing in the order of TPPNi<TPPCu≤TPPZn with their increased effective ionic radii in the square‐planar coordination. The simplicity in synthesis, the well intercolumnar organization of Col_h mesophase, the broadness of the discotic LC range, and the specific UV/Vis absorption and fluorescence emission behaviors make the symmetrically substituted fatty acid octaester porphyrins and their metal complexes very attractive for variant applications.     

Synthesis and structure of heteroleptic triple-decker neodymium,europium, holmium,erbium, and ytterbium crown phthalocyaninates

Two series of heteroleptic crown-substituted tris(phthalocyaninate) complexes (Pc)Ln[(15C5)₄Pc]Ln(Pc) and [(15C5)₄Pc]Ln[(15C5)₄Pc]Ln(Pc), where 15C5 is 15-crown-5, (Pc²⁻) is the phthalocyaninate dianion, Ln = Nd, Eu, Ho, Er, and Yb, were prepared by the reaction of tetra-15-crown-5-phthalocyanine H₂[(15C5)₄Pc] with the corresponding lanthanide acetylacetonates and lanthanum bis(phthalocyaninate) La(Pc)₂, which was used as a phthalocyaninate dianion donor. The composition and structure of the synthesized complexes were confirmed by MALDI TOF mass spectrometry, UV-Vis absorption spectroscopy, and ¹H NMR. Complete assignment of the proton resonance signals of the paramagnetic lanthanide complexes was based on analysis of lanthanide-induced shifts.     

A novel efficient approach to heteronuclear triple-decker complexes of rare earth elements with phthalocyanines

A novel approach to heteroleptic heteronuclear rare earth metal(III) trisphthalocyaninates was proposed with the complexes [(15C5)₄Pc]M*[(15C5)₄Pc]M(Pc) as examples (15C5 is 15-crown-5, Pc^2? is the phthalocyaninate dianion, and M* ?? M = Yb and Y). Unsubstituted lanthanum bisphthalocyaninate, La(Pc)₂, was used for the first time as a Pc^2? donor in the synthesis of such complexes. This substantially increased the yields of the target heteronuclear complexes over the previous literature data.     

Solvent-free synthesis,x-ray studies and in vitro inhibitory activities of copper(II) complexes of non-steroidal anti-inflammatory drugs

Solid-state mechanochemical synthesis of [Cu(CAF)₂(H₂O)(OAc)]OAc complex 1a and [Cu(COD)₂(H₂O)(OAc)]OAc complex 2a were obtained by grinding stoichiometric amounts of Cu(CH₃COO)₂·H₂O and corresponding non-steroidal anti-inflammatory drugs[(caffeine (CAF) and codeine(COD)], respectively, in a mortar with pestle. Solvent-based synthesis of 1b and 2b was also carried out by reaction of metal acetate salt and each drug by refluxing at 70 °C in CH₃OH for 1 h for comparison purposes. The complexes 1a and 2a were characterized by comparison of elemental analysis, FT-IR, UV–Vis and ¹H NMR spectra with those of the free ligand and solvent-based products (1b and 2b). The analytical and spectroscopic data of the complexes prepared via the two different methods are almost identical. X-ray diffraction patterns of the complexes prepared by mechanochemical method were different from that of the starting material suggesting formation of new metal complexes. In vitro inhibitory activities of both mechanochemical and solvent-based complexes were found to be higher than parent ligands, indicating that the antimicrobial effect of these drugs could be enhanced when they are chelated to the metal. The mechanochemical synthesis was carried out without the use of solvent or external heating. The method is faster and gives a higher yield than corresponding solvent-based reactions. The solid state reaction presented higher efficiency in terms of materials, energy and time compared to solvent-based synthesis.     

IR and Raman Vibrational Assignments for Metal-free Phthalocyanine from Density Functional B3LYP／6-31G（d） Method

Vibrational (IR and Raman) spectra for the metal-free phthalocyanine (H2Pc) have been comparatively investigated through experimental and theoretical methods. The frequencies and intensities were calculated at density functional B3LYP level using the 6-3 IG(d) basis set. The calculated vibrational frequencies were scaled by the factor 0.9613 and compared with the experimental result. In the IR spectrum, the characteristic IR band at 1008.cm^-1 is interpreted as C-N (pyrrole) in-plane bending vibration, in contrast with the traditional assigned N-H in-plane or out-of-plane bending vibration. The band at 874 cm^-1 is attributed to the isoindole deformation and aza vibration. In the Raman spectrum, the bands at 540, 566, 1310, 1340, 1425, 1448 and 1618 cm^-1 are also re-interpreted. Assignments of vibrational bands in the IR and Raman spectra are given based on density functional calculations for the first time. The present work provides valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.     

Highly Efficient Hydrophosphonylation of Aldehydes and Unactivated Ketones Catalyzed by Methylene‐Linked Pyrrolyl Rare Earth Metal Amido Complexes

A series of rare earth metal amido complexes bearing methylene‐linked pyrrolyl‐amido ligands were prepared through silylamine elimination reactions and displayed high catalytic activities in hydrophosphonylations of aldehydes and unactivated ketones under solvent‐free conditions for liquid substrates. Treatment of [(Me₃Si)₂N]₃Ln(μ‐Cl)Li(THF)₃ with 2‐(2,6‐Me₂C₆H₃NHCH₂)C₄H₃NH ( 1 , 1 equiv) in toluene afforded the corresponding trivalent rare earth metal amides of formula {(μ‐η⁵:η¹):η¹‐2‐[(2,6‐Me₂C₆H₃)NCH₂](C₄H₃N)LnN(SiMe₃)₂}₂ [Ln=Y ( 2 ), Nd ( 3 ), Sm ( 4 ), Dy ( 5 ), Yb ( 6 )] in moderate to good yields. All compounds were fully characterized by spectroscopic methods and elemental analyses. The yttrium complex was also characterized by ¹H NMR spectroscopic analyses. The structures of complexes 2 , 3 , 4 , and 6 were determined by single‐crystal X‐ray analyses. Study of the catalytic activities of the complexes showed that these rare earth metal amido complexes were excellent catalysts for hydrophosphonylations of aldehydes and unactivated ketones. The catalyzed reactions between diethyl phosphite and aldehydes in the presence of the rare earth metal amido complexes (0.1 mol %) afforded the products in high yields (up to 99 %) at room temperature in short times of 5 to 10 min. Furthermore, the catalytic addition of diethyl phosphite to unactivated ketones also afforded the products in high yields of up to 99 % with employment of low loadings (0.1 to 0.5 mol %) of the rare earth metal amido complexes at room temperature in short times of 20 min. The system works well for a wide range of unactivated aliphatic, aromatic or heteroaromatic ketones, especially for substituted benzophenones, giving the corresponding α‐hydroxy diaryl phosphonates in moderate to high yields.     

Ketimido Metallophthalocyanines: An Approach to Phthalocyanine‐Supported Mononuclear High‐Valent Ruthenium Complexes

A “metal–ketimine+ArI(OR)₂” approach has been developed for preparing metal–ketimido complexes, and ketimido ligands are found to stabilize high‐valent metallophthalocyanine (M? Pc) complexes such as ruthenium(IV) phthalocyanines. Treatment of bis(ketimine) ruthenium(II) phthalocyanines [Ru^II(Pc)(HN?CPh₂)₂] ( 1a ) and [Ru^II(Pc)(HNQu)₂] ( 1b ; HNQu=N‐phenyl‐1,4‐benzoquinonediimine) with PhI(OAc)₂ affords bis(ketimido) ruthenium(IV) phthalocyanines [Ru^IV(Pc)(N?CPh₂)₂] ( 2a ) and [Ru^IV(Pc)(NQu)₂] ( 2b ), respectively. X‐ray crystal structures of 1b and [Ru^II(Pc)(PhN?CHPh)₂] ( 1c ) show Ru? N(ketimine) distances of 2.075(4) and 2.115(3) Å, respectively. Complexes 2a , 2b readily revert to 1a , 1b upon treatment with phenols. ¹H NMR spectroscopy reveals that 2a , 2b are diamagnetic and 2b exists as two isomers, consistent with a proposed eclipsed orientation of the ketimido ligands in these ruthenium(IV) complexes. The reaction of 1a , 1b with PhI(OAc)₂ to afford 2a , 2b suggests the utility of ArI(OR)₂ as an oxidative deprotonation agent for the generation of high‐valent metal complexes featuring M? N bonds with multiple bonding characters. DFT and time‐dependent (TD)‐DFT calculations have been performed on the electronic structures and the UV/Vis absorption spectra of 1b and 2b , which provide support for the diamagnetic nature of 2b and reveal a significant barrier for rotation of the ketimido group about the Ru? N(ketimido) bond.     

Nonperipherally Octa(butyloxy)‐Substituted Phthalocyanine Derivatives with Good Crystallinity: Effects of Metal–Ligand Coordination on the Molecular Structure,Internal Structure,and Dimensions of Self‐Assembled Nanostructures

To investigate the effects of metal–ligand coordination on the molecular structure, internal structure, dimensions, and morphology of self‐assembled nanostructures, two nonperipherally octa(alkoxyl)‐substituted phthalocyanine compounds with good crystallinity, namely, metal‐free 1,4,8,11,15,18,22,25‐octa(butyloxy)phthalocyanine H₂Pc(α‐OC₄H₉)₈ ( 1 ) and its lead complex Pb[Pc(α‐OC₄H₉)₈] ( 2 ), were synthesized. Single‐crystal X‐ray diffraction analysis revealed the distorted molecular structure of metal‐free phthalocyanine with a saddle conformation. In the crystal of 2 , two monomeric molecules are linked by coordination of the Pb atom of one molecule with an aza‐nitrogen atom and its two neighboring oxygen atoms from the butyloxy substituents of another molecule, thereby forming a Pb‐connected pseudo‐double‐decker supramolecular structure with a domed conformation for the phthalocyanine ligand. The self‐assembling properties of 1 and 2 in the absence and presence of sodium ions were comparatively investigated by scanning electronic microscopy (SEM), spectroscopy, and X‐ray diffraction techniques. Intermolecular π–π interactions between metal‐free phthalocyanine molecules led to the formation of nanoribbons several micrometers in length and with an average width of approximately 100 nm, whereas the phthalocyaninato lead complex self‐assembles into nanostructures also with the ribbon morphology and micrometer length but with a different average width of approximately 150 nm depending on the π–π interactions between neighboring Pb‐connected pseudo‐double‐decker building blocks. This revealed the effect of the molecular structure (conformation) associated with metal–ligand (Pb? N_isoindole, Pb? N_aza, and Pb? O_butyloxy) coordination on the dimensions of the nanostructures. In the presence of Na⁺, additional metal–ligand (Na? N_aza and Na? O_butyloxy) coordination bonds formed between sodium atoms and aza‐nitrogen atoms and the neighboring butyloxy oxygen atoms of two metal‐free phthalocyanine molecules cooperate with the intrinsic intermolecular π–π interactions, thereby resulting in an Na‐connected pseudo‐double‐decker building block with a twisted structure for the phthalocyanine ligand, which self‐assembles into twisted nanoribbons with an average width of approximately 50 nm depending on the intertetrapyrrole π–π interaction. This is evidenced by the X‐ray diffraction analysis results for the resulting aggregates. Twisted nanoribbons with an average width of approximately 100 nm were also formed from the lead coordination compound 2 in the presence of Na⁺ with a Pb‐connected pseudo‐double‐decker as the building block due to the formation of metal–ligand (Na? N_aza and Na? O_butyloxy) coordination bonds between additionally introduced sodium ions and two phthalocyanine ligands of neighboring pseudo‐double‐decker building blocks.     

Engineering Chemically Exfoliated Large‐Area Two‐Dimensional MoS2 Nanolayers with Porphyrins for Improved Light Harvesting

Molybdenum disulfide (MoS₂) is a promising candidate for electronic and optoelectronic applications. However, its application in light harvesting has been limited in part due to crystal defects, often related to small crystallite sizes, which diminish charge separation and transfer. Here we demonstrate a surface‐engineering strategy for 2D MoS₂ to improve its photoelectrochemical properties. Chemically exfoliated large‐area MoS₂ thin films were interfaced with eight molecules from three porphyrin families: zinc(II)‐, gallium(III)‐, iron(III)‐centered, and metal‐free protoporphyrin IX (ZnPP, GaPP, FePP, H₂PP); metal‐free and zinc(II) tetra‐(N‐methyl‐4‐pyridyl)porphyrin (H₂T4, ZnT4); and metal‐free and zinc(II) tetraphenylporphyrin (H₂TPP, ZnTPP). We found that the photocurrents from MoS₂ films under visible‐light illumination are strongly dependent on the interfacial molecules and that the photocurrent enhancement is closely correlated with the highest occupied molecular orbital (HOMO) levels of the porphyrins, which suppress the recombination of electron–hole pairs in the photoexcited MoS₂ films. A maximum tenfold increase was observed for MoS₂ functionalized with ZnPP compared with pristine MoS₂ films, whereas ZnT4‐functionalized MoS₂ demonstrated small increases in photocurrent. The application of bias voltage on MoS₂ films can further promote photocurrent enhancements and control current directions. Our results suggest a facile route to render 2D MoS₂ films useful for potential high‐performance light‐harvesting applications.