Unusual Photoinduced Electron Transfer from a Zinc Porphyrin to a Tetrapyridyl Free‐Base Porphyrin in a Noncovalent Multiporphyrin Array

Excitation of the peripheral Zn porphyrin units in a noncovalent five‐porphyrin array, formed by gable‐like zinc(II) bisporphyrins and a central free‐base meso‐tetrakis(4‐pyridyl)porphyrin in a 2:1 ratio, ( ZnP₂ )₂? ( TPyP ), does not lead to a quantitative sensitization of the luminescence of the free‐base porphyrin acceptor, even though there is an effective energy transfer. Time resolution of the luminescence evidences a quenching of TPyP upon sensitization by the peripheral ZnP₂ . The time evolution of the TPyP fluorescence in the complex can be described by a bi‐exponential fitting with a major component of 180 ps and a minor one of 5 ns, compared to an isolated TPyP lifetime of 9.4 ns. The two quenched lifetimes are shown to be correlated to the presence of 2:1 and 1:1 complexes, respectively. No quenching of TPyP fluorescence occurs in ( ZnP₂ )₂?( TPyP ) at 77 K in a rigid solvent for which only an energy‐transfer process (τ=150±10 ps) from peripheral ZnP₂ to the central TPyP is observed. An unusual HOMO–HOMO electron‐transfer reaction from ZnP₂ to the excited TPyP units, responsible for the observed phenomena, is detected. The resulting charge‐separated state, ( ZnP₂ )⁺₂?( TPyP )^? is found to recombine to the ground state with a lifetime of 11 ns.     

Synthesis and Solution Studies of Silver(I)‐Assembled Porphyrin Coordination Cages

The synthesis and the characterization of two porphyrin coordination cages are reported. The design of the cage formation is based on the coordination of silver(I) ions to the pyridyl units of 3‐pyridyl appended porphyrins. ¹H/¹⁰⁹Ag NMR spectroscopy, and diffusion‐ordered spectroscopy (DOSY) experiments demonstrate that both the free base porphyrin 2H‐TPyP and the Zn‐porphyrin Zn‐TPyP form the closed cages, [ Ag₄(2H‐TPyP)₂ ]⁴⁺ and [ Ag₄(Zn‐TPyP)₂ ]⁴⁺, respectively, upon addition of two equivalents of Ag⁺. The complexation processes are characterized in details by means of absorption and emission spectroscopy in diluted CH₂Cl₂ solutions. The data are discussed in the frame of the point‐dipole exciton coupling theory; the two porphyrin monomers, in fact, experience a rigid face‐to‐face geometry in the cages and a weak inter‐porphyrin exciton coupling. An intermediate species is observed, for Zn‐TPyP , in a porphyrin/Ag⁺ stoichiometric ratio of about 1:0.5 and is tentatively ascribed to an oblique open form. The occurrence of a photoinduced electron‐transfer reaction within the cages is excluded on the basis of the experimental outcomes and thermodynamic evaluations. Photophysical experiments evidence different reactivities of singlet and triplet excited states in the assemblies. A lower fluorescence quantum yield and triplet formation is discussed in relation to the constrained geometry of the complexes. Unusually long triplet excited state lifetimes are measured for the assemblies.     

Coordination and hydrogen‐bonding assemblies in hybrid reaction products between 5,10,15,20‐tetra‐4‐pyridylporphyrin and dysprosium trinitrate hexahydrate

Reactions of the title free‐base porphyrin compound (TPyP) with dysprosium trinitrate hexahydrate in different crystallization environments yielded two solid products, viz. [μ‐5,15‐bis(pyridin‐1‐ium‐4‐yl)‐10,20‐di‐4‐pyridylporphyrin]bis[aquatetranitratodysprosium(III)] benzene solvate, [Dy₂(NO₃)₈(C₄₀H₂₈N₈)(H₂O)₂]·C₆H₆, (I), and 5,10,15,20‐tetrakis(pyridin‐1‐ium‐4‐yl)porphyrin pentaaquadinitratodysprosate(III) pentanitrate diethanol solvate dihydrate, (C₄₀H₃₀N₈)[Dy(NO₃)₂(H₂O)₅](NO₃)₅·2C₂H₆O·2H₂O, (II). Compound (I) represents a 2:1 metal–porphyrin coordinated complex, which lies across a centre of inversion. Two trans‐related pyridyl groups are involved in Dy coordination. The two other pyridyl substituents are protonated and involved in intermolecular hydrogen bonding along with the metal‐coordinated water and nitrate ligands. Compound (II) represents an extended hydrogen‐bonded assembly between the tetrakis(pyridin‐1‐ium‐4‐yl)porphyrin tetracation, the [Dy(NO₃)₂(H₂O)₅]⁺ cation and the free nitrate ions, as well as the ethanol and water solvent molecules. This report provides the first structural characterization of the exocyclic dysprosium complex with tetrapyridylporphyrin. It also demonstrates that charge balance can be readily achieved by protonation of the peripheral pyridyl functions, which then enhances their capacity in hydrogen bonding as H‐atom donors rather than H‐atom acceptors.     

Encapsulation of Metalloporphyrins in a Self‐Assembled Cubic M8L6 Cage: A New Molecular Flask for Cobalt–Porphyrin‐Catalysed Radical‐Type Reactions

The synthesis of a new, cubic M₈L₆ cage is described. This new assembly was characterised by using NMR spectroscopy, DOSY, TGA, MS, and molecular modelling techniques. Interestingly, the enlarged cavity size of this new supramolecular assembly allows the selective encapsulation of tetra(4‐pyridyl)metalloporphyrins (M^II(TPyP), M=Zn, Co). The obtained encapsulated cobalt–porphyrin embedded in the cubic zinc–porphyrin assembly is the first example of a catalytically active encapsulated transition‐metal complex in a cubic M₈L₆ cage. The substrate accessibility of this system was demonstrated through radical‐trapping experiments, and its catalytic activity was demonstrated in two different radical‐type transformations. The reactivity of the encapsulated Co^II(TPyP) complex is significantly increased compared to free Co^II(TPyP) and other cobalt–porphyrin complexes. The reactions catalysed by this system are the first examples of cobalt–porphyrin‐catalysed radical‐type transformations involving diazo compounds which occur inside a supramolecular cage.     

Guest‐Induced Photophysical Property Switching of Artificial Light‐Harvesting Dendrimers

An artificial light‐harvesting multiporphyrin dendrimer ( 8P_ZnP_FB ) composed of a focal freebase porphyrin ( P_FB ) with eight zinc(II) porphyrin ( P_Zn ) wings exhibited unique photophysical property switching in response to specific guest molecule binding. UV/Vis titration studies indicated stable 1:2 host–guest complex formation between 8P_ZnP_FB and meso‐tetrakis(4‐pyridyl)‐porphyrin ( TPyP ) for which the first and second association constants were estimated to be >10⁸ M ^?1 and 3.0×10⁷ M ^?1, respectively. 8P_ZnP_FB originally shows 94 % energy transfer efficiency from P_Zn to the focal P_FB . By the formation of the host–guest complex ( 8P_ZnP_FB? 2 TPyP ) the emission intensity of 8P_ZnP_FB is significantly decreased, and an ultrafast charge separation state is generated. The energy transfer process from P_Zn wings to the P_FB core in 8P_ZnP_FB is almost entirely switched to an electron transfer process by the formation of 8P_ZnP_FB? 2 TPyP .     

Dynamic Assembly Inclusion Complexes of Tweezer‐type Bis(zinc porphyrin) with 5,15‐Di(4‐pyridyl)porphyrin Derivatives

Dynamic assembly inclusion complexes of tweezer-type bis(zinc porphyrin) (1) with di(4-pyridyl)porphyrin derivatives have been designed and constructed. The complexes are induced by Zn-N coordination, and the weak binding allows the large-size di(4-pyridyl)porphyrin guests in random rotation. Dynamic characteristics of these assemblies, such as ligand exchange and dynamic fluorescence quenching, have been investigated by 1H NMR, UV-Vis and fluorescence spectra. The stability of such assembly has pronounced dependence on the size-matching effect and thermal effect.     

Exploring Supramolecular Self‐Assembly of Tetraarylporphyrins by Halogen Bonding: Crystal Engineering with Diversely Functionalized Six‐Coordinate Tin(L)2–Porphyrin Tectons

This study targets the construction of porphyrin assemblies directed by halogen bonds, by utilizing a series of purposely synthesized Sn(axial ligand)₂–(5,10,15,20‐tetraarylporphyrin) [Sn(L)₂‐TArP] complexes as building units. The porphyrin moiety and the axial ligands in these compounds contain different combinations of complimentary molecular recognition functions. The former bears p‐iodophenyl, p‐bromophenyl, 4′‐pyridyl, or 3′‐pyridyl substituents at the meso positions of the porphyrin ring. The latter comprises either a carboxylate or hydroxy anchor for attachment to the porphyrin‐inserted tin ion and a pyridyl‐, benzotriazole‐, or halophenyl‐type aromatic residue as the potential binding site. The various complexes were structurally analyzed by single‐crystal X‐ray diffraction, accompanied by computational modeling evaluations. Halogen‐bonding interactions between the lateral aryl substituents of one unit of the porphyrin complex and the axial ligands of neighboring moieties was successfully expressed in several of the resulting samples. Their occurrence is affected by structural (for example, specific geometry of the six‐coordinate complexes) and electronic effects (for example, charge densities and electrostatic potentials). The shortest intermolecular I???N halogen‐bonding distance of 2.991 Å was observed between iodophenyl (porphyrin) and benzotriazole (axial ligand) moieties. Manifestation of halogen bonds in these relatively bulky compounds without further activation of the halophenyl donor groups by electron‐withdrawing substituents is particularly remarkable.     

Metallierung und C‐C‐Kupplung von 2‐Pyridylmethylamin: Synthese und Strukturen von Methylzink‐2‐pyridylmethylamid,Tris(trimethylsilyl)methylzink‐2‐pyridylmethylamid und (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethen

Metalation and C‐C Coupling Reaction of 2‐Pyridylmethylamine: Synthesis and Structures of Methylzinc‐2‐pyridylmethylamide, Tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide and (Z)‐1‐Amino‐1,2‐bis(2‐pyridyl)ethene The metalation of 2‐pyridylmethylamine with dimethylzinc yields methylzinc‐2‐pyridylmethylamide ( 1 ), which shows a dimer‐trimer equilibrium in solution. Compound 1 crystallizes trimeric with a Zn₃N₃‐cycle in boat conformation. The endocyclic Zn‐N distances vary between 202 and 206 pm. Heating of this compound in toluene in the presence of dimethylzinc leads to the precipitation of zinc metal and to the formation of a few crystals of bis—[methylzinc‐2‐pyridylmethylamido]‐N, N′‐bis(methylzinc)‐2,3,5,6—tetrakis(2‐pyridyl)‐1,4‐diazacyclohexane ( 2 ). The protolysis of this solution with acetamide gives yellowish (Z)‐1‐amino‐1,2‐dipyridylethene ( 3 ) in a rather poor yield. The enamine tautomer is stabilized by N‐H···N hydrogen bridges. The demanding tris(trimethylsilyl)methyl group at the zinc atom allows the isolation of the dimeric tris(trimethylsilyl)methylzinc‐2‐pyridylmethylamide (4) ₂ in good yield. A C‐C coupling reaction of this compound with dimethylzinc is not possible.     

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.     

Substituted 2,2′‐Bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyl Complexes of Zinc

The condensation reaction of 2,2′‐diamino‐4,4′‐dimethyl‐6,6'‐dibromo‐1,1′‐biphenyl with 2‐hydroxybenzaldehyde as well as 5‐methoxy‐, 4‐methoxy‐, and 3‐methoxy‐2‐hydroxybenzaldehyde yields 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyl ( 1a ) as well as the 5‐, 4‐, and 3‐methoxy‐substituted derivatives 1b , 1c , and 1d , respectively. Deprotonation of substituted 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls with diethylzinc yields the corresponding substituted zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls ( 2 ) or zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyls ( 3 ). Recrystallization from a mixture of CH₂Cl₂ and methanol can lead to the formation of methanol adducts. The methanol ligands can either bind as Lewis base to the central zinc atom or as Lewis acid via a weak O–H ··· O hydrogen bridge to a phenoxide moiety. Methanol‐free complexes precipitate as dimers with central Zn₂O₂ rings.     

Dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate and bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ2N,N′)copper(I) tetrafluoroborate

The single‐crystal X‐ray structures of dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate, C₁₄H₁₂N₂O₄, and the copper(I) coordination complex bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ²N,N′)copper(I) tetrafluoroborate, [Cu(C₁₄H₁₂N₂O₄)₂]BF₄, are reported. The uncoordinated ligand crystallizes across an inversion centre and adopts the anticipated anti pyridyl arrangement with coplanar pyridyl rings. In contrast, upon coordination of copper(I), the ligand adopts an arrangement of pyridyl donors facilitating chelating metal coordination and an increased inter‐pyridyl twisting within each ligand. The distortion of each ligand contrasts with comparable copper(I) complexes of unfunctionalized 2,2′‐bipyridine.     

A one‐dimensional zinc(II) coordination polymer incorporating [1,1′‐biphenyl]‐4,4′‐dicarboxylate and N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide ligands

In the title compound, catena‐poly[[[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]chloridozinc(II)]‐μ‐[1,1′‐biphenyl]‐4,4′‐dicarboxylato‐[[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]chloridozinc(II)]‐μ‐[N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide]], [Zn₂(C₁₄H₈O₄)Cl₂(C₂₆H₂₂N₄O₂)₃]_n, the Zn^II centre is four‐coordinate and approximately tetrahedral, bonding to one carboxylate O atom from a bidentate bridging dianionic [1,1′‐biphenyl]‐4,4′‐dicarboxylate ligand, to two pyridine N atoms from two N,N′‐bis(pyridin‐3‐ylmethyl)‐[1,1′‐biphenyl]‐4,4′‐dicarboxamide ligands and to one chloride ligand. The pyridyl ligands exhibit bidentate bridging and monodentate terminal coordination modes. The bidentate bridging pyridyl ligand and the bridging [1,1′‐biphenyl]‐4,4′‐dicarboxylate ligand both lie on special positions, with inversion centres at the mid‐points of their central C—C bonds. These bridging groups link the Zn^II centres into a one‐dimensional tape structure that propagates along the crystallographic b direction. The tapes are interlinked into a two‐dimensional layer in the ab plane through N—H...O hydrogen bonds between the monodentate ligands. In addition, the thermal stability and solid‐state photoluminescence properties of the title compound are reported.     

Effect of Solvent and Protonation/Deprotonation on Electrochemistry,Spectroelectrochemistry and Electron‐Transfer Mechanisms of N‐Confused Tetraarylporphyrins in Nonaqueous Media

A series of N‐confused free‐base meso‐substituted tetraarylporphyrins was investigated by electrochemistry and spectroelectrochemistry in nonaqueous media containing 0.1 M tetra‐n‐butylammonium perchlorate (TBAP) and added acid or base. The investigated compounds are represented as (XPh)₄NcpH₂, in which “Ncp” is the N‐confused porphyrin macrocycle and X is a OCH₃, CH₃, H, or Cl substituent on the para position of each meso‐phenyl ring of the macrocycle. Two distinct types of UV/Vis spectra are initially observed depending upon solvent, one corresponding to an inner‐2H form and the other to an inner‐3H form of the porphyrin. Both forms have an inverted pyrrole with a carbon inside the cavity and a nitrogen on the periphery of the π‐system. Each porphyrin undergoes multiple irreversible reductions and oxidations. The first one‐electron addition and first one‐electron abstraction are located on the porphyrin π‐ring system to give π‐anion and π‐cation radicals with a potential separation of 1.52 to 1.65 V between the two processes, but both electrogenerated products are unstable and undergo a rapid chemical reaction to give new electroactive species, which were characterized in the present study. The effect of the solvent and protonation/deprotonation reactions on the UV/Vis spectra, redox potentials and reduction/oxidation mechanisms is discussed with comparisons made to data and mechanisms for the structurally related free‐base corroles and porphyrins.     

Flat vs. Folded Chelate Rings in cis‐PtIIa2 (a = NH3, a2 = en,a2 = 2, 2′‐bpy) Complexes of Twofold Substituted Diazine Ligands

Acid‐base and ligating properties of three bis(substituted)pyrazine (pz) and pyrimidine (pym) ligands (pyrazine‐2, 5‐dicarboxylic acid, 2, 5‐pzdcH2, 2, 3‐bis(pyridine‐2‐yl)pyrazine, 2, 3‐bppz, pyrimidine‐4, 6‐dicarboxylic acid, 4, 6‐pmdcH₂) toward cis‐Pt^IIa₂ (a = NH₃, a₂ = en, a₂ = 2, 2′‐bpy) have been studied. Combinations of pz‐N/pym‐N with donor atoms of the substituents lead to 5‐membered platinum chelates, but exclusive N, N‐coordination through the pyridyl substituents of 2, 3‐bppz can lead to a 7‐membered platinum chelate with a characteristic L‐shape of the resulting cation. It is observed for Pt^II(2, 2′‐bpy), yet not for Pt^II(en), and is a consequence of differences in sterical interactions between the 2, 3‐bppz ligand and the coligands of Pt^II.     

Controlled Growth of Porphyrin Wires at a Solid‐Liquid Interface

Bis(zinc porphyrin) scaffolds bearing C₈ or C₁₈ alkyl chains and imidazole end groups self‐assembled in a head‐to‐tail fashion into multi‐porphyrin assemblies on both HOPG and mica. Due to weaker molecule surface‐interactions, longer arrays formed on mica than on HOPG. In both cases, it was essential first to generate monomers that were drop casted on the surface, then to allow time for the bis(zinc porphyrins) to assemble. Although thicker fibrous assemblies were observed with the C₈ alkyl substituents than with the longer chains, noncovalent assemblies up to 1 μm long were observed for each molecule. These investigations provide a reproducible, noncovalent method to grow porphyrin arrays that may be of interest in molecular electronics for charge transport.     

Chemical Fixation of CO2 and Other Heterogeneous Catalytic Studies by Employing a Layered Cu‐Porphyrin Prepared Through Single‐Crystal to Single‐Crystal Exchange of a Zn Analogue

A solvothermal reaction of Zn(NO₃)₂ ? 6 H₂O, tetra‐(4‐pyridyl)porphyrin (H₂TPyP), and 4,4′‐oxybis(benzoic acid) (H₂OBA) resulted in a new two‐dimensional Zn‐ porphyrin metal–organic framework compound, [Zn₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₆ ( 1 ; DMA=N,N‐dimethylacetamide). The Zn^II ions present in 1 could be exchanged by using a solution of Cu(NO₃)₂ ? 3 H₂O in DMA at room temperature to give [Cu₂(C₄₀H₂₄N₈)_0.5(C₁₄H₈O₅)(DMA)](DMA)(H₂O)₃ ( Cu∈1 ). The extra‐framework solvent molecules have been shown to be reversibly removed or exchanged without collapse of the framework. Solvent‐free Cu∈1 was explored as an active heterogeneous catalyst towards three different organic reactions: 1) the chemical fixation of CO₂ into cyclic carbonate at room temperature and 1 atm; 2) the nitroaldol reaction under solvent‐free conditions, and 3) the three‐component coupling of aminopyridine, benzaldehyde, and aryl alkynes followed by 5‐exo‐dig cyclization to produce the important pharmacophore imidazopyridine.     

New self-assemblies with zinc meso-tetra[3-(1H-imidazol-1-yl)phenyl] porphyrin for use in supramolecular solar cells

In this work, a new zinc meso-tetra[3-(1H-imidazol-1-yl)phenyl]porphyrin (ZnP) was synthesized. Further, the porphyrin ZnP was immobilized by metal-ligand axial coordination (ZnP-A) and a metal-ligand edged binding approach (ZnP-Zn-A) on the nanostructured TiO₂ electrode surface modified with coordinating ligand functionality, isonicotinic acid (A). The performances of the assemblies-sensitized solar cells were performed under irradiance of 100 mW?cm^?2 AM 1.5G sunlight. Photo-electrochemical studies reveal significantly improved performance of the assembly ZnP-A. These assemblies can afford a fertile base for further design and fabrication of new supramolecular solar cells in future.     

A Functionalized Spiro[chlorin‐porphyrin]‐Type ‘Dimer’ Dizinc Complex from Rapid [4+2] Self‐cycloaddition of a Conjugated [β,β′‐Bis(methylene)porphyrinato]zinc

Thermal extrusion of SO₂ from β,β′‐sulfolenoporphyrins is an effective method for in situ generation of β,β′‐bis(methylene)porphyrin which remained unobserved in typical synthetic applications but underwent quickly efficient [4+2]‐cycloaddition reactions with dienophiles.We now report the thermal extrusion of SO₂ from the symmetrical (tetra‐β,β′‐sulfolenoporphyrinato)zinc 1?Zn in the absence of a dienophile (Scheme). In the event, the thermally in situ generated conjugated diene underwent a [4+2] self‐cycloaddition, to give the {spirobi[tri‐β,β′‐sulfolenoporphyrinato]}dizinc 4?2Zn . This chiral (racemic) spirobiporphyrinoid dizinc complex represents the combination of the closely positioned and interacting chromophores of a (porphyrinato)zinc and of a (β‐methylene‐β,β′‐dihydroporphyrinato)zinc. It carries six sulfoleno moieties that are still available for further SO₂ extrusion and cycloaddition reactions.     

Ab initio investigation of 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole for the design of efficient organic field‐effect transistors

The initial molecular structure of 2,2′‐bis(4‐trifluoromethylphenyl)‐ 5,5′‐bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron λ_e, the reorganization energy of hole λ_h, adiabatic electron affinity (EA_a), vertical electron affinity (EA_v), adiabatic ionization potential (IP_a), and vertical ionization potential (IP_v) using DFT. Based on the evaluation of hole reorganization energy, λ_h, and electron reorganization energy, λ_e, it has been predicted that 2,2′‐bis(4‐trifluoromethylphenyl)‐5,5′‐bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field‐effect transistors. © 2015 Wiley Periodicals, Inc.     

Carbon‐bridged Oligo(phenylenevinylene)s as Light‐harvesting Antenna for Porphyrins

The efficacy of carbon‐bridged oligo(phenylenevinylenes)s (COPVs) as light‐harvesting antenna for porphyrins is demonstrated using a series of 5,15‐di‐COPVn‐substituted free‐base and zinc porphyrins, COPVn‐MP‐COPVn (n=1–3, M=H₂, Zn). These molecules were synthesized by Suzuki–Miyaura cross‐coupling reactions of COPVn‐Bpin and Br‐H₂P‐Br . The absorption spectra of these compounds in solution show a significant expansion of the Soret band region together with a bathochromic shift of the Q band, suggesting a significant interaction between these chromophores in the ground state. The photoluminescence quantum yield of the porphyrin‐COPV conjugates is enhanced up to four times relative to the parent porphyrins. Theoretical calculations also indicated interactions between these chromophores in the HOMO, which suggests that the light‐harvesting ability stems from the expansion of the π‐electron‐conjugation system.