Porphyrin Dimers Research Articles

Singly and Doubly 1,2-Phenylene-Inserted Porphyrin Arch-Tape Dimers: Synthesis and Highly Contorted Structures.

Singly and doubly 1,2-phenylene-inserted NiII porphyrin arch-tape dimers 3 and 9 were synthesized from the corresponding β-to-β 1,2-phenylene-bridged NiII porphyrin dimers 5 and 11 via Ni0 -mediated reductive cyclization and DDQ/Sc(OTf)3 -promoted oxidative cyclization as key steps, respectively. Owing to the fused eight-membered ring(s), 3 showed a more contorted structure than those of previously reported arch-tape dimers 2 a and 2 b possessing a fused seven-membered ring. Furthermore, 9 displayed much larger molecular contortion. As the molecular contortion increases, the Q band of the absorption spectrum becomes more red-shifted and the electrochemcial HOMO-LUMO gap becomes smaller, reaching at 1294 nm and 0.77 eV in 9, respectively. The effect of molecular contortion on the electronic properties was studied by means of DFT calculations.

Theoretical characterization of supramolecular complexes formed by fullerenes and dimeric porphyrins

Intramolecular stacking is very strong in dimeric porphyrins. However, in solution they are able to inhibit folding and can trap fullerenes with very high association constants. Diabatic interaction energies can be a useful approach to evaluate the strength of porphyrin/fullerene supramolecular complexes.

Molecular brakes based on the Zn(ii) porphyrin dimer

The rotational movement of molecular brakes based on two Zn–porphyrin units interconnected by a spacer may be reversibly locked by addition of an external auxiliary ligand.

Improved conversion efficiency of 10% for solid-state dye-sensitized solar cells utilizing P-type semiconducting CuI and multi-dye consisting of novel porphyrin dimer and organic dyes

To realize highly efficient solid-state dye-sensitized solar cells (SDSCs), the absorption range of the dye should be extended to the near-IR range to increase short-circuit current density (Jsc); a high Jsc in turn requires a highly conductive p-type semiconductor.

Tailored homo- and hetero- lanthanide porphyrin dimers: a synthetic strategy for integrating multiple spintronic functionalities into a single molecule.

We present the design, synthesis and magnetic properties of molecular magnetic systems that contain all elements necessary for spin-valve control in molecular spintronic devices in a single molecule. We investigate the static and dynamic magnetic properties and quantum spin properties of butadiyne-linked homo- and hetero-nuclear lanthanide-porphyrin dimers. A heterometallated porphyrin dimer containing both TbIII and DyIII centres is created rationally by the stepwise oxidative homocoupling of distinct lanthanide-porphyrin monomers. TbIII and DyIII mononuclear porphyrin complexes, homodimers and heterodimers all exhibit slow magnetic relaxation below 10 kelvin under a static magnetic field. The coherence times for GdIII porphyrin monomers and dimers are found to be in excess of 3.0 μs at 2 K, allowing distinct magnetic manipulations in low temperature transport experiments.

Cofacial porphyrin dimers assembled from N-heterocyclic carbene–metal bonds

A porphyrin bearing four imidazolium rings on the meso positions was used as an N-heterocyclic carbene (NHC) precursor for the synthesis of porphyrin dimers with face-to-face orientations. The porphyrins are connected through the formation of eight M-CNHC bonds, with M = AgI or AuI.

Unusual solvent polarity dependent excitation relaxation dynamics of a bis[p-ethynyldithiobenzoato]Pd-linked bis[(porphinato)zinc] complex

A porphyrin dimer linked by a Pd(ii)-based linker displays unusual excited-state dynamics where solvent polarity steers singlet and triplet decay-channel population.

Screening of different interactions in oxo-manganese porphyrin dimers containing axial N-donor ligands: a theoretical study.

A theoretical analysis for describing the dimeric assemblies of high-valent manganese(v)-oxo meso-tetraphenylporphyrin (TPP) ([(TPP)MnVO]22+) and meso-tetrakis(pentafluorophenyl)porphyrin (TPFPP) ([(TPFPP)MnVO]22+) in the presence of axial N-donor ligands is presented. Our theoretical results revealed two types interactions in dimers: a sandwich-like interaction between phenyl rings of porphyrin molecules, and a non-bonded T-shape interaction between nitrogen donors attached to Mn centers. The curvature in the geometry of porphyrin in the [(TPP)MnVO]22+/N-donor system is significantly smaller than that of [(TPFPP)MnVO]22+/N-donor system. Moreover, the Mn–N(ax) distances in [(TPFPP)MnVO]22+/N-donor system are shorter than those of [(TPP)MnVO]22+/N-donor system. Also, the donor–acceptor interaction between the imidazoles and the Mn centers are stronger than those of the other ligands in both porphyrins. These results are supported by atoms in molecules (AIM) and natural bond orbital (NBO) analysis.

Interfacing tetrapyridyl-C60 with porphyrin dimers via π-conjugated bridges: artificial photosynthetic systems with ultrafast charge separation.

We report on the synthesis, characterization and photophysical properties of a donor-bridge-acceptor supramolecular hybrid system, consisting of a tetrapyridyl fullerene derivative (C60-tpyr) as electron acceptor, with the four pyridyl groups as part of oligophenyleneethynylene/phenylenevinylene bridges, and zinc porphyrin dimers (ZnP)2 as electron donor species. Based on the metal-to-ligand coordination between the zinc metal centers of (ZnP)2 and the four pyridyl entities of C60-tpyr, a strong binding constant (5 × 105 M-1) for the formation of C60-tpyr·[(ZnP)2]2 was evidenced. Insights into the electronic interactions between the photoactive (ZnP)2 units and C60-tpyr emanated from complementary physicochemical assays, which were further supported by theoretical calculations. Notably, the absorption and emission titration assays revealed strong interactions between the electron donor and acceptor species within C60-tpyr·[(ZnP)2]2, both in the ground and excited state. Moreover, femtosecond and nanosecond laser photolysis transient absorption measurements were performed and provided solid evidence for intramolecular electron transfer processes derived from the singlet excited state of (ZnP)2 to C60-tpyr. Comparison with systems in which either four monomeric zinc porphyrins (ZnP) were complexed with C60-tpyr or a (ZnP)2 was coordinated with a dipyridylfullerene revealed the beneficial role of C60-tpyr in increasing the lifetime of charge-separation.

A low-bandgap dimeric porphyrin molecule for 10% efficiency solar cells with small photon energy loss

SVA treatment induces π–π stacking and tightens lamellar packing of porphyrin molecules and also improves phase purity of blend films which enhance the exciton separation and reduce the recombination.

High-detectivity panchromatic photodetectors for the near infrared region based on a dimeric porphyrin small molecule

A dimeric porphyrin-based photodetector shows a strong spectral response at 1000 nm with a detectivity of 1013Jones at zero bias.

Dimeric Porphyrin Small Molecules for Efficient Organic Solar Cells with High Photoelectron Response in the Near-Infrared Region.

Small molecules (SMs) with elongated backbones are promising for achieving a higher photovoltaic performance. Herein, a dimeric porphyrin small molecule, ZnP2-DPP, consisting of two porphyrin units linked with an ethynylene as the core and two diketopyrrolopyrrole (DPP) units as the arms is designed and synthesized as an electron donor for solution-processed bulk-heterojunction (BHJ) organic solar cells (OSCs). A significantly enhanced power conversion efficiency of 8.45% with an impressive short-circuit current density (Jsc) up to 19.65 mA cm-2 is achieved for the BHJ OSCs based on ZnP2-DPP under AM 1.5G irradiation (100 mW cm-2) compared to that for the OSCs based on the dimeric porphyrin linked with bis-ethynylenes reported previously. Furthermore, the devices show broad photoelectron responses up to 1000 nm with high near-infrared external quantum efficiency up to 66% at 780 nm. This is the first study reporting SM OSCs displaying such a large Jsc of about 20 mA cm-2 simultaneously with a considerably high and deep photoelectron response of up to 1000 nm.

Chemical Stimulus-responsive Folding and Unfolding of a Dendrimeric Assembly.

A dendrimeric trimer undergoes folding and unfolding in response to a chemical stimulus. The trimer of interest contains a central dendrimer with a butadiyne-linked zinc porphyrin dimer ((ZnP)2 ) core, in addition to two terminal dendrimers with zinc porphyrin (ZnP) cores. The obtained absorption spectra indicate that the unfolded form is the exclusive conformer in chloroform, while the addition of 1,4-diazabicyclo[2.2.2]octane (DABCO) in chloroform leads to transformation from the unfolded to the folded structure containing two DABCO units per trimer; the folded structure originates from the cross-linking of (ZnP)2 and ZnP with DABCO. Moreover, the addition of excess DABCO promotes the generation of the unfolded structure containing four DABCO units.

Disulfide-bridge dimeric porphyrin and their reference compounds for glutathione-based specific tumor-activation

The tumor micro-environment is rich in glutathione. To exploit this feature for tumor-activatable porphyrin-based photosensitizers, a dimeric disulfide-bridged porphyrin has been designed and prepared, together with two reference derivatives, a non-cleavable dimer and a monomer. The three compounds have been investigated from a photochemical and photophysical point of view. It appears that the disulfide-bridged derivative exhibited intramolecular aggregation, but to an insufficient extent to induce a satisfying self-quenching of its photoproperties. Unlike expected, the non-cleavable dimer behaved like the monomeric derivative, due to the superior flexibility of the alkyl bridge over the disulfide bridge.

Synthesis and Study at a Solid/Liquid Interface of Porphyrin Dimers Linked by Metal Ions.

Several porphyrin dimers linked by metal ions were prepared. One trimeric compound was also isolated and one porphyrin dimer linked by palladium(II) could be structurally characterized. In solution, the size of the new compounds was estimated by DOSY NMR techniques. These compounds all contained long aliphatic chains (O-C12H25), which were used to assemble them at a highly oriented pyrolytic graphite (HOPG)/liquid interface. The highly ordered arrays were visualized by scanning tunneling microscopy (STM).

Photoresponsive Electrodes Modified with DNA Duplexes Possessing a Porphyrin Dimer.

This work describes the formation of a porphyrin (Por) dimer using a DNA duplex as a scaffold and photocurrent generation from electrodes modified with a monolayer of Por-DNA conjugates. The solid-phase click reaction between an azide-porphyrin and oligonucleotide labeled with an ethynyl group on CPG support was utilized to conjugate the Por to the DNA. UV/Vis absorption and circular dichroism (CD) spectral studies revealed that the Por dimer can be formed through DNA hybridization and that through-space electronic interactions, characterized from the exciton-coupled absorption and the bisignate CD, can occur between the two Por molecules. Photoelectrochemical experiments were performed for the electrodes functionalized with a monolayer composed of the Por-DNA conjugates. It was found that the Por dimer on the electrode, which was designed to resemble the special pair in natural photosynthesis, shows efficient photocurrent generation in the presence of electron-acceptor reagents compared with the Por monomer. These findings strongly support the idea that the DNA structures could be useful to construct Por arrays, which is essential for the design of photo- and bio-electronic devices.

Trace Oxygen Sensitive Material Based on Two Porphyrin Derivatives in a Heterodimeric Complex.

The successful preparation of a novel dimer complex formed between 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-porphyrin Fe(III) chloride and (5,10,15,20-tetraphenylporphinato) dichlorophosphorus(V) chloride using the well-known reactivity of the P–X bond is reported. The obtained complex was characterized by UV-vis, Fourier transform infrared spectroscopy (FT-IR), fluorescence, 1H-NMR, 13C-NMR, and 31P-NMR spectroscopic techniques and also by additional Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple Bond Correlation (HMBC) experiments in order to correctly assign the NMR signals. Scanning electron microscopy (SEM) and EDX quantifications completed the characterizations. This novel porphyrin dimer complex demonstrated fluorescence sensing of H2O2 in water for low oxygen concentrations in the range of 40–90 µM proving medical relevance for early diagnosis of diseases such as Alzheimer’s, Parkinson’s, Huntington’s, and even cancer because higher concentrations of H2O2 than 50 μM are consideredcytotoxic for life. Due to its optical properties, this novel metalloporphyrin–porphyrin based complex is expected to show PDT and bactericidal activity under visible-light irradiation.

Photophysical Properties of Porphyrin Dimer–Single-Walled Carbon Nanotube Linked Systems

Porphyrin dimers were covalently grafted onto electron-accepting single-walled carbon nanotube (SWNT) sidewalls by direct aryl radical addition reaction with an m- or p-phenylene linker with the help of π–π interaction between the porphyrins. A splitting of the porphyrin Soret band and DFT calculations supported the selective formation of the porphyrin dimers on the sidewall of SWNTs. Photoexcitation of the porphyrin dimers on the SWNT resulted in the formation of the exciplex state, which directly decayed to the ground state without yielding the complete charge-separated state. Lifetimes of the porphyrin dimer–SWNT exciplex were longer than that of a porphyrin monomer–SWNT exciplex due to the stabilization by π-electron interaction over two porphyrin rings. In addition, the weaker electronic coupling through the meta-linkage than the para-one may be responsible for the exciplex lifetime of the porphyrin dimer–SWNT with the m-phenylene linker (49 ps) longer than that with the p-phenylene one (24 ps). The ...

Dynamic Molecular Invasion into a Multiply Interlocked Catenane

AbstractA multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine can move along the alkyl chains, it acts as an adjustable wall, thus permitting the invasion of large molecules into the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both nanospaces with high affinity. A photometric titration experiment revealed the two‐step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin–spin interaction was switched off by the intercalation of dianionic porphyrins.

Dynamic Molecular Invasion into a Multiply Interlocked Catenane.

A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine can move along the alkyl chains, it acts as an adjustable wall, thus permitting the invasion of large molecules into the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both nanospaces with high affinity. A photometric titration experiment revealed the two-step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin-spin interaction was switched off by the intercalation of dianionic porphyrins.