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Probing the origin of fluorescence quenching of graphene-porphyrin hybrid material
We report transient absorption spectroscopic studies on the hybrid material composed of porphyrin molecules covalently attached to graphene for investigating the mechanism underlying the reported fluorescence quenching of porphyrin in the hybrid [1]. Excited state dynamics of pure graphene suspension and porphyrin have also been studied as reference samples. A fast excited state decay was observed in the hybrid
Electron-transport properties of ethyne-bridged diphenyl zinc-porphyrin molecules
We investigate the electron-transport properties of ethyne-bridged diphenyl
zinc-porphyrin molecules suspended between gold (111) electrodes by
first-principles calculations within the framework of density functional
theory. It is found that the conductance of a molecular junction in which
phenyl and porphyrin rings are perpendicular is reduced by three orders of
magnitude compared with that of a junction in which the phenyl and porphyrin
rings are coplanar. In the coplanar configuration, electrons are transmitted
through states, which extend over the whole molecule. In the
perpendicular configuration, the conductance is suppressed because of the
reduction of electron hopping between states of the phenyl ring and
states of the porphyrin ring.Comment: 11 page
New two in one magnetic fluorescent nanocomposites
Magnetite nanoparticles have been coated by a porphyrin derivative to produce new magnetic materials with fluorescent properties. The magnetic nanoparticles were prepared using two different methods, one based on sol-gel techniques and ultrasonic processing, and the other via a controlled chemical co-precipitation. Different types of porphyrin functionalised magnetic nanoparticles have been prepared and have been characterised by electron microscopy (TEM and SEM), XRD, FTIR, Raman, UV-vis, and fluorescence spectroscopy. Microscopy results showed the formation of core-shell nanostructures, with IR and photoluminescence spectroscopy results confirming the presence of porphyrin in the shell
Understanding the mechanism stabilizing intermediate spin states in Fe(II)-Porphyrin
Spin fluctuations in Fe(II)-porphyrins are at the heart of heme-proteins
functionality. Despite significant progress in porphyrin chemistry, the
mechanisms that rule spin state stabilisation remain elusive. Here, it is
demonstrated by using multiconfigurational quantum chemical approaches,
including the novel Stochastic-CASSCF method, that electron delocalization
between the metal centre and the pi system of the macrocycle differentially
stabilises the triplet spin states over the quintet. This delocalisation takes
place via charge-transfer excitations, involving the out-of-plane iron d
orbitals, key linking orbitals between metal and macrocycle. Through a
correlated breathing mechanism, the 3d electrons can make transitions towards
the pi orbitals of the macrocycle. This guarantees a strong coupling between
the on-site radial correlation on the metal and electron delocalization.
Opposite-spin 3d electrons of the triplet can effectively reduce electron
repulsion in this manner. Constraining the out-of-plane orbitals from breathing
hinders delocalization and reverses the spin ordering. Our results find a
qualitative analogue in Kekul\'e resonance structures involving also the metal
centre
Urinary porphyrin excretion in hepatitis C infection
A high prevalence of hepatitis C virus infection in porphyria cutanea tarda in some populations suggests a close link between viral hepatitis and alteration of porphyrin metabolism. Moreover, there is evidence of a role of porphyrinopathies in hepatocarcinogenesis. The aim of our study was to obtain data on the prevalence and patterns of heme metabolism alterations in patients with chronic hepatitis C virus infection. Urinary porphyrin excretion was prospectively studied in 100 consecutive outpatients with chronic hepatitis C infection without signs of photosensitivity, using an ion-pair high performance liquid chromatography method. Increased total porphyrin excretion was found in 41 patients, with predominant excretion of coproporphyrins (whole study group: mean 146 mu g/g creatinine, interquartile range 76-186; normal <150), in 10 patients excretion exceeded 300 mu g/g creatinine. In the majority of all patients studied (75/100) an increased ratio of the relatively hydrophobic coproporphyrin isomer I to isomer III was found. In just one case, urinary porphyrin pattern characteristic for chronic hepatic porphyria was present (uroporphyrin > coproporphyrin, heptacarboxyporphyrin III increased) but the total porphyrin excretion was only slightly elevated in this case. In the whole group, total urinary porphyrin excretion correlated well with serum bilirubin and was inversely correlated with albumin and thrombin time. In conclusion, secondary coproporphyrinuria occurs frequently in heptatitis C infection, whereas in Germany, preclinical porphyria cutanea tarda seems to be rare in these patients
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A low-bandgap dimeric porphyrin molecule for 10% efficiency solar cells with small photon energy loss
Dimeric porphyrin molecules have great potential as donor materials for high performance bulk heterojunction organic solar cells (OSCs). Recently reported dimeric porphyrins bridged by ethynylenes showed power conversion efficiencies (PCEs) of more than 8%. In this study, we design and synthesize a new conjugated dimeric D-A porphyrin ZnP2BT-RH, in which the two porphyrin units are linked by an electron accepting benzothiadiazole (BT) unit. The introduction of the BT unit enhances the electron delocalization, resulting in a lower highest occupied molecular orbital (HOMO) energy level and an increased molar extinction coefficient in the near-infrared (NIR) region. The bulk heterojunction solar cells with ZnP2BT-RH as the donor material exhibit a high PCE of up to 10% with a low energy loss (Eloss) of only 0.56 eV. The 10% PCE is the highest for porphyrin-based OSCs with a conventional structure, and this Eloss is also the smallest among those reported for small molecule-based OSCs with a PCE higher than 10% to date
PET/PDT theranostics: Synthesis and biological evaluation of a peptide-targeted gallium porphyrin
The development of novel theranostic agents is an important step in the pathway towards personalised medicine, with the combination of diagnostic and therapeutic modalities into a single treatment agent naturally lending itself to the optimisation and personalisation of treatment. In pursuit of the goal of a molecular theranostic suitable for use as a PET radiotracer and a photosensitiser for PDT, a novel radiolabelled peptide–porphyrin conjugate targeting the α6β1-integrin has been developed. 69/71Ga and 68Ga labelling of an azide-functionalised porphyrin has been carried out in excellent yields, with subsequent bioconjugation to an alkyne-functionalised peptide demonstrated. α6β1-integrin expression of two cell lines has been evaluated by flow cytometry, and therapeutic potential of the conjugate demonstrated. Evaluation of the phototoxicity of the porphyrin–peptide theranostic conjugate in comparison to an untargeted control porphyrin in vitro, demonstrated significantly enhanced activity for a cell line with higher α6β1-integrin expression when compared with a cell line exhibiting lower α6β1-integrin expression
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