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We report the successful heteroepitaxial growth of perfectly oriented hybrid MOF thin films. By employing step-by-step liquid-phase epitaxy (LPE), [Zn2(ndc)2(dabco)]nwas grown on [Cu2(ndc)2(dabco)]n, thus demonstrating that the MOF-on-MOF deposition scheme developed for powdered microcrystalline MOF materials can also be applied in connection with LPE for MOF thin films or multilayers. The deposition was monitored by surface plasmon resonance (SPR) spectroscopy, the resulting MOF heterostructures were characterized using IR spectroscopy and different types of X-ray diffraction (XRD)-based techniques. The results suggest that the LPE method is a promising way to fabricate and grow MOF heterostructures, and also demonstrates the potential of [Cu2(ndc)2(dabco)]nMOF thin films as substrates for the LPE-based growth of different MOFs on top. [ABSTRACT FROM AUTHOR]

Chalcogenide-based thin-film solar cell optimized for rear illumination and used for CO2 reduction is presented. Central to this innovation is a thinner, Cu(In,Ga)S2 chalcopyrite absorber coated with a robust metallic top layer, which potentially surpasses the performance of conventional front-illuminated designs. Using cobalt quaterpyridine molecular catalyst, photocurrent densities for CO2 reduction exceeding 10 mA/cm2 at 0.0 V vs. RHE under 1 Sun illumination, and ca. 16 mA/cm2 at -0.25 V vs. RHE were achieved in voltammetry experiments. Controlled potential electrolysis showed catalytic activity over 20 h with selectivity for CO ranging from > 92% (first 4 hours) to 86% at the end of the experiment. This approach opens limitless possibilities for employing various reduction catalysts, extending far beyond CO2 reduction. It imposes minimal constraints on absorption properties, immobilization methods, and catalyst nature, setting the stage for high-performance, adaptable PEC devices., (© 2024 Wiley‐VCH GmbH.)

In photo-induced charge separation, organic thin films with donor and acceptor chromophores are vital for uses such as artificial photosynthesis and photodetection. The main challenges include optimizing charge separation efficiency and identifying the ideal acceptor/donor ratio. Achieving this is difficult due to the variability in molecular configurations within these typically amorphous organic aggregates. Metal-organic frameworks (MOFs) provide a structured solution by enabling systematic design of donor/acceptor blends with adjustable ratios within a crystalline lattice. We demonstrate this approach by incorporating donor and acceptor naphthalenediimide (NDI) chromophores as linkers in a highly oriented, monolithic MOF thin film. By adjusting the NDI acceptor linker concentration during the layer-by-layer assembly of surface-anchored MOF thin films (SURMOFs), we significantly enhanced charge separation efficiency. Surprisingly, the optimum acceptor concentration was only 3 %, achieving a forty-fold increase in photodetection efficiency compared to baseline NDI donor-based SURMOFs. This unexpected behaviour was clarified through theoretical analysis enabled by the well-defined crystalline structure of the SURMOFs. Using density functional theory and kinetic Monte Carlo simulations, we identified two opposing effects from acceptors: the positive effect of suppressing undesirable charge carrier recombination is offset at high concentrations by a reduction in charge-carrier mobility., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Despite excellent optical and electrical properties, the brittleness of indium tin oxide (ITO), used as a transparent electrode, prevents the realization of stable flexible devices. If silver nanowire (AgNW) networks represent a promising alternative, their lack of thermal and electrochemical stability still prevents their fast development in numerous applications. Herein, we report a novel strategy consisting of the deposition of an electrochromic and protective layer of oriented hybrid materials, also known as surface-anchored metal-organic frameworks (SurMOFs). Furthermore, the dual role played by the SurMOF is achieved using a room-temperature and low-cost method for the efficient use of bare AgNWs. A step forward was achieved by demonstrating electrochemical and mechanical stability for flexible electrochromic SurMOF@AgNW/PET thin films, switching reversibly from orange (+0.2 V) to blue (-0.8 V) in 8.4 s and 10.4 s, respectively, with a color efficiency of 158 cm 2 /C after being bent 300 times.

We present two novel cobalt pyridyldiimine complexes functionalized with pyrene. Initially modest in homogeneous acetonitrile solution, their electrocatalytic CO 2 reduction performance significantly improves upon immobilization on MWCNTs in an aqueous carbonate buffer. The complexes exhibit outstanding stability, with CO selectivity exceeding 97%, and TON and TOF values reaching up to 10 4 and above 1.2 s -1 , respectively.

Phthalocyanines have been described as effective photosensitizers for photodynamic therapy and are therefore, being studied for their biomedical applications. The metalation of photosensitizers can improve their photodynamic therapy potential. Here, we focus on the biological properties of [1,4-Bis(3,6,9,12-Tetraoxatridec-1-yloxy)phthalocyaninato]zinc(II) (ZnPc(αEG 4 ) 2 ) and demonstrate its exceptional anticancer activity upon light stimulation to kill preferentially cancer cells with a start of efficiency at 10 pM. Indeed, in this work we highlighted the high selectivity of ZnPc(αEG 4 ) 2 for cancer cells compared with healthy ones and we establish its mechanism of action, enabling us to conclude that ZnPc(αEG 4 ) 2 could be a powerful tool for cancer therapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Centre Nationale de Recherche Scientifique. Published by Elsevier B.V. All rights reserved.)

Dye-sensitized photocatalytic systems (DSPs) have been extensively investigated for solar-driven hydrogen (H 2 ) evolution. However, their application in carbon dioxide (CO 2 ) reduction remains limited. Furthermore, current solar-driven CO 2 -to-CO DSPs typically employ rhenium complexes as catalysts. In this study, we have developed DSPs that incorporate noble metal-free components, specifically a zinc-porphyrin as photosensitizer (PS) and a cobalt-quaterpyridine as catalyst (CAT). Taking a significant stride forward, we have achieved an antenna effect for the first time in CO 2 -to-CO DSPs by introducing a Bodipy as an additional chromophore to enhance light harvesting efficiency. The energy transfer from Bodipy to zinc porphyrin resulted in remarkable stability (turn over number (TON)=759 vs. CAT), and high CO evolution activity (42 mmol g -1  h -1 vs. CAT)., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

There is a growing interest in developing dye-sensitized photocatalytic systems (DSPs) to produce molecular hydrogen (H 2 ) as alternative energy source. To improve the sustainability of this technology, we replaced the sacrificial electron donor (SED), typically an expensive and polluting chemical, with an alcohol oxidation catalyst. This study demonstrates the first dye-sensitized system using a diketopyrrolopyrrole dye covalently linked to 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) based catalyst for simultaneous H 2 evolution and alcohol-to-aldehyde transformation operating in water with visible irradiation., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Metal-organic frameworks (MOFs) featuring redox activity are highly appealing for electrocatalytic or charge accumulation applications. An important aspect in this field is the ability to address as many redox centers as possible in the material by an efficient diffusion of charges. Herein, we investigate for the first time the charge diffusion processes occurring upon two sequential one-electron reductions in an MOF thin film. Two pyrazolate-zinc(II)-based MOFs including highly electro-deficient perylene diimide (PDI) ligands were grown on conducting substrates, affording thin films with double n -type electrochromic properties as characterized by spectroelectrochemical analysis. In depth electrochemical and chronoabsorptiometric investigations were carried out to probe the charge diffusion in the MOF layers and highlighted significant differences in terms of diffusion kinetics and material stability between the first and second successive reduction of the redox-active PDI linkers. Our results show that MOFs based on multiredox centers are more sensitive to encumbrance-related issues than their monoredox analogues in the context of electrochemical applications, an observation that further underlines the fundamental aspect of careful pore dimensions toward efficient and fast ion diffusion.

Drug-targeted delivery has become a top priority in the world of medicine in order to develop more efficient therapeutic agents. This is important as a critical underlying problem in cancer therapy stems from the inability to deliver active therapeutic substances directly to tumor cells without causing collateral damage. In this work, zinc(II) phthalocyanine (ZnPc) was selected as a sensitizer and was linked to different targeting agents, which would be recognized by overexpressed proteins in cancer cells. As targeting agents, we first selected the two ligands ( DAA1106 ,  PK11195 ) of the translocator protein ( TSPO ) and then  Erlotinib  a binding group of the ATP domain of tyrosine kinase in epidermal growth factor (EGFR). ZnPc was connected via an ethylene glycol chain to either one ( n = 1) or four ( n = 4) targeting agents. The biological activity of these conjugates ZnPc(ligand) n was investigated on MDA-MB-231 breast human cancer cells and human hepatoma HepG2 cells, first in the dark (cytotoxicity) and then under irradiation (photodynamic therapy). The dark cytotoxicity was extremely low (IC 50 ≥ 50 μM) for all of these compounds, which is a required criterion for further photodynamic application. After irradiation at 650 nm, only the conjugates bearing one targeting ligand such as ZnPc-[DAA1106]1, ZnPc-[PK11195]1, and ZnPc-[Erlo]1 showed photodynamic activity, while those linked to 4 targeting agents were inactive. Importantly, fluorescence imaging microscopy showed the colocalization of ZnPc-[DAA1106]1, ZnPc-[PK11195]1 and ZnPc-[erlo]1, at mitochondria, a result that justifies the observed photodynamic activity of these conjugates. This study first shows the impact of the number and the mode of organization of targeting agents on the ability of the sensitizer to cross the cell membrane. When zinc(II) phthalocyanine carries a single targeting agent, a significant photodynamic activity on MDA-MB-231 breast human cancer cells was measured and localization at the mitochondria was demonstrated by fluorescence imaging, thus proving the potential of the sensitizer linked to a targeting agent to improve selectivity. Another important conclusion from this study for the design of future effective PDT drugs using multivalence effects is to control the arrangement of the targeting agents in order to design molecules that will be able to pass the cell membrane barriers.

Control of charge separation and recombination is critical for dye-sensitized solar cells and photoelectrochemical cells, and for p-type cells, the latter process limits their photovoltaic performance. We speculated that the lateral electron hopping between dyes on a p-type semiconductor surface can effectively separate electrons and holes in space and retard recombination. Thus, device designs where lateral electron hopping is promoted can lead to enhanced cell performance. Herein, we present an indirect proof by involving a second dye to monitor the effect of electron hopping after hole injection into the semiconductor. In mesoporous NiO films sensitized with peryleneimide (PMI) or naphthalene diimide (NDI) dyes, dye excitation led to ultrafast hole injection into NiO from either excited PMI* (τ < 200 fs) or NDI* (τ = 1.2 ps). In cosensitized films, surface electron transfer from PMI - to NDI was rapid (τ = 24 ps). Interestingly, the subsequent charge recombination (ps-μs) with NiO holes was much slower when NDI - was generated by electron transfer from PMI - than when NDI was excited directly. We therefore indicate that the charge recombination is slowed down after the charge hopping from the original PMI sites to the NDI sites. The experimental results supported our hypothesis and revealed important information on the charge carrier kinetics for the dye-sensitized NiO photoelectrode system.

We report the synthesis and the in depth electrochemical study of two novel electron accepting sulfonated perylene diimide pyrazolate ligands. Bridging the sulfone moieties of the perylene core unexpectedly affected the optical and electronic properties as evidenced by spectroelectrochemical investigation. Notably, we achieved a significant lowering of the LUMO level to -4.83 eV, ranking the ligand among the best electron acceptors via a straightforward synthetic procedure. These ligands can be foreseen for the development of n-type functional materials.

Metal-organic frameworks (MOFs) built from different building units offer functionalities going far beyond gas storage and separation. In connection with advanced applications, e.g., in optoelectronics, hierarchical MOF-on-MOF structures fabricated using sophisticated methodologies have recently become particularly attractive. Here, we demonstrate that the structural complexity of MOF-based architectures can be further increased by employing highly spatioselective photochemistry. Using a layer-by-layer, quasi-epitaxial synthesis method, we realized a photoactive MOF-on-MOF hetero-bilayer consisting of a porphyrinic bottom layer and a tetraphenylethylene (TPE)-based top layer. Illumination of the monolithic thin film with visible light in the presence of oxygen gas results in the generation of reactive oxygen species ( 1 O 2 ) in the porphyrinic bottom layer, which lead to a photocleavage of the TPE units at the internal interface. We demonstrate that this spatioselective photochemistry can be utilized to delaminate the top layers, yielding two-dimensional (2D) MOF sheets with well-defined thickness. Experiments using atomic force microscopy (AFM) demonstrate that these platelets can be transferred onto other substrates, thus opening up the possibility of fabricating planar MOF structures using photolithography.

Photoelectrochemical cells based on semiconductors are among the most studied methods of artificial photosynthesis. This study concerns the immobilization, on a mesoporous conducting indium tin oxide electrode (nano-ITO), of a molecular triad (NDADI-P-Ru-TEMPO) composed of a ruthenium tris-bipyridine complex (Ru) as photosensitizer, connected at one end to 2,2,6,6-tetramethyl-1-piperidine N-oxyl (TEMPO) as alcohol oxidation catalyst and at the other end to the electron acceptor naphthalenedicarboxyanhydride dicarboximide (NDADI). Light irradiation of NDADI-P-Ru-TEMPO grafted to nano-ITO in a pH 10 carbonate buffer effects selective oxidation of para-methoxybenzyl alcohol (MeO-BA) to para-methoxybenzaldehyde with a TON of approximately 150 after 1 h of photolysis at a bias of 0.4 V vs. SCE. The faradaic efficiency is found to be of 80±5 %. The photophysical study indicates that photoinduced electron transfer from the Ru complex to NDADI is a slow process and must compete with direct electron injection into ITO to have a better performing system. This work sheds light on some of the important ways to design more efficient molecular systems for the preparation of photoelectrocatalytic cells based on catalyst-dye-acceptor arrays immobilized on conducting electrodes., (© 2021 Wiley-VCH GmbH.)

The combination of photodynamic therapy and chemotherapy is a promising strategy to enhance cancer therapeutic efficacy and reduce drug resistance. In this study two zinc(II) phthalocyanine-tin(IV) conjugates linked by a triethylene glycol chain were synthesized and characterized. In these complexes, the zinc(II) phthalocyanine was used as a potential photosensitizer for PDT and the tin complex was selected as cytostatic moiety. The two dyads composed of zinc(II) phthalocyanine and tin complexes exhibited high cytotoxicity, in absence of light stimulation, against MCF-7 human breast cancer cells with low LC 50 values in the range of 0.016-0.453 µM. In addition, these complexes showed superior cytotoxicity than their mixture of equimolar component, accompanied with a higher activity towards cancer cells compared to human healthy fibroblasts. However, under irradiation of the zinc phthalocyanine unit (at 650 nm) no photodynamic activity could be detected, due to the most likely quenching of zinc(II) phthalocyanine singlet excited state by the nearby tin complex according to a photoinduced electron transfer process. This study demonstrates the potential of heterometallic anticancer chemotherapeutics composed of a zinc phthalocyanine and tin complex, and it highlights that the development of such conjugates requires that the sensitizer preserves its photophysical properties and in particular its singlet oxygen sensitization ability in the conjugate in order to combine the PDT activity with the cytotoxicity of the anticancer drug.

The discovery of novel anticancer chemotherapeutics is fundamental to treat cancer more efficiently. Towards this goal, two dyads consisting of a gold porphyrin appended to organotin(iv) entities were synthesized and their physicochemical and biological properties were characterized. One dyad contains a gold porphyrin connected to a tin(iv) cation via a malonate and two phenyl ligands (AuP-SnPh 2 ), while the other contains two tin(iv) cations each chelated to one carboxylic acid group of the malonate and three phenyl ligands (AuP-Sn 2 Ph 6 ). The mode of chelation of Sn(iv) to the malonate was elucidated by IR spectroscopy and 119 Sn NMR. In the solid state, the complexes exist as coordination polymers in which the tin is penta-coordinated and bridged to two different malonate units. In solution the chemical shifts of 119 Sn signals indicate that the tin complexes are in the form of monomeric species associated with a tetra-coordinated tin cation. The therapeutic potential of these new compounds was assessed by determining their cytotoxic activities on human breast cancer cells (MCF-7) and on healthy human fibroblasts (FS 20-68). The study reveals that the dyads are more potent anticancer drugs than the mixture of their individual components (gold porphyrin and reference tin complexes). Therefore, the covalent link of organotin complexes to a gold porphyrin induces a synergistic cytotoxic effect. The dyad AuP-SnPh 2 shows high cytotoxicity (0.13 μM) against MCF-7 along with good selectivity for cancer cells versus healthy cells. Finally, it was also shown that the dyad AuP-Sn 2 Ph 6 exhibits a very high anticancer activity (LC 50 = 0.024 μM), but the presence of two tin units induces strong cytotoxicity on healthy cells too (LC 50 = 0.032 μM). This study underscores, thus, the potential of the association of gold porphyrin and organotin complexes to develop anticancer metallo-drugs.

Several photophysical properties of chromophores depend crucially on intermolecular interactions. Thermally-activated delayed fluorescence (TADF) is often influenced by close packing of the chromophore assembly. In this context, the metal-organic framework (MOF) approach has several advantages: it can be used to steer aggregation such that the orientation within aggregated structures can be predicted using rational approaches. We demonstrate this design concept for a DPA-TPE (diphenylamine-tetraphenylethylene) chromophore, which is non-emissive in its solvated state due to vibrational quenching. Turning this DPA-TPE into a ditopic linker makes it possible to grow oriented MOF thin films exhibiting pronounced green electroluminescence with low onset voltages. Measurements at different temperatures clearly demonstrate the presence of TADF. Finally, this work reports that the layer-by-layer process used for MOF thin film deposition allows the integration of the TADF-DPA-TPE in a functioning LED device., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Artificial photosynthesis is a vibrant field of research aiming at converting abundant, low energy molecules such as water, nitrogen or carbon dioxide into fuels or useful chemicals by means of solar energy input. Photo-electrochemical reduction of carbon dioxide is an appealing strategy, aiming at reducing the greenhouse gas into valuable products such as carbon monoxide at low or without bias voltage. Yet, in such configuration, there is no catalytic system able to produce carbon monoxide selectively in aqueous media with high activity, and using earth-abundant molecular catalyst. Upon associating a p-type Cu(In,Ga)Se 2 semi-conductor with cobalt quaterpyridine complex, we herein report a photocathode complying with the aforementioned requirements. Pure carbon dioxide dissolved in aqueous solution (pH 6.8) is converted to carbon monoxide under visible light illumination with partial current density above 3 mA cm -2 and 97% selectivity, showing good stability over time.

Recently, gold(III) porphyrins have gained great interest as anticancer drugs not only for the stability of gold(III) but also for the functionalization of the porphyrin to allow bridging with another metal such as platinum(II). We report here, for the first time, the synthesis of three new bimetal compounds containing a gold(III) porphyrin conjugated to a platinum diamine moiety through malonate bridging to obtain enhanced cytotoxicity from both metals combined with the phototoxicity of the porphyrin. The three complexes differ in the type of diamine ligand around platinum(II): ammonia (NH 3 ), cyclohexanediamine (CyDA), and pyridylmethylamine (Py). The synthesis was carried out using the complexation of activated malonic acid derivatives with aquadiaminoplatinum(II) complexes, and the products were characterized by IR, NMR, mass spectra, and elementary analysis. The cytotoxic activity of the conjugates was screened in both healthy cell lines and cancer cell lines, human fibroblast cells (FS-68) and human breast cancer cells (MCF-7), and was compared to that of the corresponding platinum(II) complexes. The cyclohexyldiamine (CyDA) derivative exhibited the greatest cytotoxic effect among the series. The results showed that Au(III)/Pt(II) conjugates are more potent by 2-5.6-fold than the corresponding platinum complexes. Moreover, the dyad AuP-PtCyDA is 18% more potent and also more selective toward cancer cells than the parent gold porphyrin substituted with malonic acid. On the other hand, the IC 50 of the dyad AuP-PtCyDA is 43% lower than that of AuTPP but is more selective toward healthy cells. Singlet oxygen measurements indicated that gold(III) porphyrin derivatives are poor oxygen sensitizers and cell death occurred potentially due to generation of other reactive oxygen species (ROS) upon reductive quenching of the gold porphyrin excited state. In addition, the increase in cancer cell death obtained after light irradiation is totally absent in healthy cells, demonstrating the specificity of this PDT treatment on cancer cells. Our findings imply that the incorporation of two different cytotoxic metals in the same molecule represents a remarkable cytotoxic effect in comparison to traditional homometallic Pt(II) drugs.

In molecular solids, the intense photoluminescence (PL) observed for solvated dye molecules is often suppressed by nonradiative decay processes introduced by excitonic coupling to adjacent chromophores. We have developed a strategy to avoid this undesirable PL quenching by optimizing the chromophore packing. We integrated the photoactive compounds into metal-organic frameworks (MOFs) and tuned the molecular alignment by introducing adjustable "steric control units" (SCUs). We determined the optimal alignment of core-substituted naphthalenediimides (cNDIs) to yield highly emissive J-aggregates by a computational analysis. Then, we created a large library of handle-equipped MOF chromophoric linkers and computationally screened for the best SCUs. A thorough photophysical characterization confirmed the formation of J-aggregates with bright green emission, with unprecedented photoluminescent quantum yields for crystalline NDI-based materials. This data demonstrates the viability of MOF-based crystal engineering approaches that can be universally applied to tailor the photophysical properties of organic semiconductor materials.

An ideal material for photon harvesting must allow control of the exciton diffusion length and directionality. This is necessary in order to guide excitons to a reaction center, where their energy can drive a desired process. To reach this goal both of the following are required; short- and long-range structural order in the material and a detailed understanding of the excitonic transport. Here we present a strategy to realize crystalline chromophore assemblies with bespoke architecture. We demonstrate this approach by assembling anthracene dibenzoic acid chromophore into a highly anisotropic, crystalline structure using a layer-by-layer process. We observe two different types of photoexcited states; one monomer-related, the other excimer-related. By incorporating energy-accepting chromophores in this crystalline assembly at different positions, we demonstrate the highly anisotropic motion of the excimer-related state along the [010] direction of the chromophore assembly. In contrast, this anisotropic effect is inefficient for the monomer-related excited state.

Photochemical reactions typically proceed via multiple reaction pathways, yielding a variety of isomers and products. Enhancing the selectivity is challenging. Now, the potential of supramolecular control for oxidative photocyclization of a tetraarylethylene, containing a stereogenic -C=C- bond, is demonstrated. In solution, this photochemical reaction produces three constitutional isomers (substituted phenanthrenes), with slow kinetics. When the reactant is assembled into a crystalline framework, only one product forms with accelerated kinetics. Key to this selectivity enhancement is the integration into a surface grown metal-organic framework (SURMOF); the dramatic gain in selectivity is ascribed to the hindrance of the rotational freedom of the -C=C- double bond. The structure of the MOF is key; the corresponding reaction in the solid does not result in such a high increase in selectivity. A striking change of luminescence properties after photocyclization is observed., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

When chromophores are brought into close proximity, noncovalent interactions (π-π/CH-π) can lead to the formation of excitonically coupled states, which bestow new photophysical properties upon the aggregates. Because the properties of the new states not only depend on the strength of intermolecular interactions, but also on the relative orientation, supramolecular assemblies, where these parameters can be varied in a deliberate fashion, provide novel possibilities for the control of photophysical properties. This work reports that core-substituted naphthalene diimides (cNDIs) can be incorporated into surface-mounted metal- organic structures/frameworks (SURMOFs) to yield optical properties strikingly different from conventional aggregates of such molecules, for example, formed in solution or by crystallization. Organic linkers are used, based on cNDIs, well-known organic chromophores with numerous applications in different optoelectronic devices, to fabricate MOF thin films on transparent substrates. A thorough characterization of the properties of these highly ordered chromophoric assemblies reveals the presence of non-emissive excited states in the crystalline material. Structural modulations provide further insights into the nature of the coupling that gives rise to an excited-state energy level in the periodic structure., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new carbon monoxide (CO)-releasing material has been developed by embedding a manganese carbonyl complex, MnBr(bpydc)(CO) 3 (bpydc = 5,5'-dicarboxylate-2,2'-bipyridine) into a highly robust Zr(iv)-based metal-organic framework (MOF). Efficient and controllable CO-release was achieved under exposure to low intensity visible light. Size-controllable nanocrystals of the photoactive MOF were obtained and their CO-releasing properties were correlated with their crystal sizes. The photoactive crystals were processed into cellular substrates with a biocompatible polymer matrix, and the light-induced delivery of CO and its subsequent cellular uptake were monitored using a fluorescent CO-probe. The results discussed here demonstrate a new opportunity to use MOFs as macromolecular scaffolds towards CO-releasing materials and the advantage of MOFs for high CO payloads, which is essential in future therapeutic applications.

The upbuilding of dirhodium tetracarboxylate paddlewheels into porous architectures is still challenging because of the inertness of equatorial carboxylates for ligand-exchange reaction. Here we demonstrate the synthesis of a new family of metal-organic cuboctahedra by connecting dirhodium units through 1,3-benzenedicarboxylate and assembling cuboctahedra as porous solids. Carbon monoxide and nitric oxide were strongly trapped in the internal cavity thanks to the strong affinity of unsaturated axial coordination sites of dirhodium centers.

The development of nitric oxide (NO) releasing materials has been of significant importance due to their application in cell biology and biomedicine. Besides the macromolecular scaffold dangling NO releasing moiety, porous materials have been used to host such NO releasing molecules. Here we synthesized a series of porous coordination polymers (PCPs), in which N-nitrosamine functional groups as photoactive NO donors were introduced into the framework scaffolds by post-synthetic nitrosation of amine functionalized analogous PCPs. We further demonstrated a controlled release of NO from the PCPs by light irradiation. Though isoreticular frameworks based on octanuclear clusters of titanium or aluminium ions were chosen due to their water-stability, the frameworks showed difference in stability in cell culture media; while aluminium frameworks were less stable in water and physiological media, the titanium analogue was highly stable even under physiological conditions.

The assembly of metal ions with organic ligands through the formation of coordination bonds gives crystalline framework materials, known as metal-organic frameworks (MOFs), which recently emerged as a new class of porous materials. Besides the structural designability of MOFs at the molecular length scale, the researchers in this field very recently made important advances in creating more complex architectures at the mesoscopic/macroscopic scale, in which MOF nanocrystals are used as building units to construct higher-order superstructures. The structuring of MOFs in such a hierarchical order certainly opens a new opportunity to improve the material performance via design of the physical form rather than altering the chemical component. This review highlights these superstructures and their applications by categorizing them into four dimensionalities, zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) superstructures. Because the key issue for structuring of MOFs is to spatially control the nucleation process in desired locations, this review conceptually categorizes the available synthetic methodologies from the viewpoint of the reaction system.

Structural transformability accompanied by molecular accommodation is a distinguished feature of porous coordination polymers (PCPs) among porous materials. Conventional X-ray crystallography allows for the determination of each structural phase emerged during transformation. However, the propagation mechanism of transformation through an entire crystal still remains in question. Here we elucidate the structural nature of the spatial transient state, in which two different but correlated framework structures, an original phase and a deformed phase, simultaneously exist in one crystal. The deformed phase is distinctively generated only at the crystal surface region by introducing large guest molecules, while the remaining part of crystal containing small molecules maintains the original phase. By means of grazing incidence diffraction techniques we determine that the framework is sheared with sharing one edge of the original primitive cubic structure, leading to the formation of crystal domains with four mirror image relationships.

Besides conventional approaches for regulating in-coming molecules for gas storage, separation, or molecular sensing, the control of molecular release from the pores is a prerequisite for extending the range of their application, such as drug delivery. Herein, we report the fabrication of a new porous coordination polymer (PCP)-based composite consisting of a gold nanorod (GNR) used as an optical switch and PCP crystals for controlled molecular release using light irradiation as an external trigger. The delicate core-shell structures of this new platform, composed of an individual GNR core and an aluminum-based PCP shell, were achieved by the selective deposition of an aluminum precursor onto the surface of GNR followed by the replication of the precursor into aluminum-based PCPs. The mesoscopic structure was characterized by electron microscopy, energy dispersive X-ray elemental mapping, and sorption experiments. Combination at the nanoscale of the high storage capacity of PCPs with the photothermal properties of GNRs resulted in the implementation of unique motion-induced molecular release, triggered by the highly efficient conversion of optical energy into heat that occurs when the GNRs are irradiated into their plasmon band. Temporal control of the molecular release was demonstrated with anthracene as a guest molecule and fluorescent probe by means of fluorescence spectroscopy.

Functional cellular substrates for localized cell stimulation by small molecules provide an opportunity to control and monitor cell signalling networks chemically in time and space. However, despite improvements in the controlled delivery of bioactive compounds, the precise localization of gaseous biomolecules at the single-cell level remains challenging. Here we target nitric oxide, a crucial signalling molecule with site-specific and concentration-dependent activities, and we report a synthetic strategy for developing spatiotemporally controllable nitric oxide-releasing platforms based on photoactive porous coordination polymers. By organizing molecules with poor reactivity into polymer structures, we observe increased photoreactivity and adjustable release using light irradiation. We embed photoactive polymer crystals in a biocompatible matrix and achieve precisely controlled nitric oxide delivery at the cellular level via localized two-photon laser activation. The biological relevance of the exogenous nitric oxide produced by this strategy is evidenced by an intracellular change in calcium concentration, mediated by nitric oxide-responsive plasma membrane channel proteins.

The synthesis, photophysical characterization and energy-transfer features of a series of hybrid truxene derivatives peripherally decorated with inorganic Os-containing polypyridine units and organic Bodipy dyes are reported. The photoactive terminal units are coupled to the central truxene scaffold by rigid ethynyl linkers in a star-shaped arrangement. The absorption range widely covers the UV-Vis spectrum and the Os (3)MLCT or the Bodipy triplet act as final collectors of the absorbed energy.

The design of crystal morphology, or exposed crystal facets, has enabled the development (e.g., catalytic activities, material attributes, and oriented film formation) of porous coordination polymers (PCPs) without changing material compositions. However, because crystal growth mechanisms are not fully understood, control of crystal morphology still remains challenging. Herein, we report the morphology design of [Cu(3)(btc)(2)](n) (btc = benzene-1,3,5-tricarboxylate) by the coordination modulation method (modulator = n-dodecanoic acid or lauric acid). A morphological transition (octahedron-cuboctahedron-cube) in the [Cu(3)(btc)(2)](n) crystal was observed with an increase in concentration of the modulator. By suitably defining a coarse-grained standard unit of [Cu(3)(btc)(2)](n) as its cuboctahedron main pore and determining its attachment energy on crystal surfaces, Monte Carlo coarse-grain modeling revealed the population and orientation of carboxylates and elucidated an important role of the modulator in determining the <100>- and <111>-growth throughout the crystal growth process. This comprehension, in fact, successfully led to designed crystal morphologies with oriented growth on bare substrates. Because selective crystal orientations on the bare substrates were governed by crystal morphology, this contribution also casts a new light on the unexplored issue of the significance of morphology design of PCPs.

A new strategy to synthesize monodispersed porous coordination polymer (PCP) nanocrystals at room temperature was developed and utilized for the formation of PCP thin films on gold substrates with fine control over the crystal sizes using the coordination modulation method. Hybridization of these PCP thin films with an environment-controlled quartz crystal microbalance system allowed determining the adsorption properties for organic vapors (methanol and hexane). In the case of high sensitivity (at the low-concentration dosing of analytes), the sensor response depended on the crystal size but not on the type of analyte. In contrast, at the high-concentration dosing, a clear dependence of the sorption kinetics on the analyte was observed due to significant sorbate-sorbate interaction., (© 2011 American Chemical Society)

A rigid star-shaped tetrachromophoric trimetallic complex engineered from a 5,5',10,10',15,15'-hexabutyltruxene platform functionalized in the 2,7,12 positions with three different metal centers, namely, a terpyridine-Pt(II) ethynylene unit and Ru(II) and Os(II) bipyridine centers, was synthesized in a controlled fashion and characterized by (1)H NMR and mass spectrometry. The protocol was devised in such a way that key mono and dinuclear model complexes and two reference truxene ligands could also be prepared. Room temperature (RT) optical absorption and RT and 77 K luminescence studies were performed on the truxene ligands, the trimetallic species, the various mono- and binuclear complexes and precursors lacking the truxene fragment; RT nanosecond transient absorption measurements were also carried out in particular cases. The electronic properties of the Ru and Os subunits in the arrays were found to be unaffected by the presence of the truxene core whereas direct linking of the Pt subunit to the truxene via the σ-alkyne bond markedly influences the spectroscopic behavior of the Pt center. Remarkably the truxene phosphorescence was clearly established in the two ligands (lifetime of 4.3 s for the mono ethynyl-bipy substituted truxene and 17.5 ms for the bis ethynyl-bipy substituted truxene) and also detected in the Pt-containing complexes PtL' (model Pt-truxene) and Pt-Os (Pt-truxene-Os dyad) at low temperature. This is attributed to the closeness in energy of the Pt (3)CT level and the truxene triplet at low temperature and to the spin-orbit coupling induced by the Pt heavy atom. Transient absorbance measurements evidenced the population of the Pt-based triplet in the Pt-truxene mononuclear complex PtL' at room-temperature. For the trimetallic complex, where the various centers exhibit an energy gradient for the local excited levels, and following an approach based on the use of selected excitation of the components, an initial energy transfer was found to occur from the central truxene unit toward the peripheral Pt, Ru, and Os metal-based centers. Subsequent Pt-based and Ru-based excited state depletion contributes to the final sensitization of the low-lying Os triplet excited state; the excited state dynamics for these multicascade processes are examined in detail.

We report on the synthesis, optical properties and energy-transfer features of a series of transition-metal-containing complexes and dyads, based on a pre-organised truxene scaffold. In this series, the [Ru(bpy)(3)](2+) and [Os(bpy)(3)](2+) photoactive terminals are coupled to the bridging aromatic truxene core through rigid ethynyl linkers. The photoinduced energy-transfer processes taking place from the Ru- to the Os-based levels, and from the truxene bridging ligand to the terminal-metal chromophores are studied and the pathways and mechanisms are discussed. The photoinduced energy-transfer process observed in the dyad proceeds rapidly through: i) an efficient (1)L-->(1)Os direct energy transfer followed by intersystem crossing to (3)Os, and ii) a fast (1)L-->(1)Ru energy-transfer step and subsequent intersystem crossing to (3)Ru followed by a (3)Ru-->(3)Os energy-transfer process. The first (1)L-->(1)Os and (1)L-->(1)Ru steps are controlled by a dipole-dipole interaction (Förster mechanism), whereas the subsequent (3)Ru-->(3)Os step proceeds by means of a long-range (approximately 24 A) through-bond mediated Dexter mechanism, facilitated by the conjugation along the bpy-truxene-bpy molecular axis.

Two functional ethynyl-pyrene derivatives have been designed and synthesized by di- and tetra-substitutions of bromo pyrene derivatives with N-(4-ethynylphenyl)-3,4,5-tris(hexadecyloxy)benzamide fragments. The photoluminescence wavelength of the pyrene core can be tuned by the substitution pattern and the state of matter (solid, solution, gel, or liquid crystal). The disubstituted pyrene derivative 1 is not mesomorphic but produces robust and highly fluorescent gels in DMF, toluene, and cyclohexane. The well-defined fibers and ropes of the gel states were characterized by SEM and laser scanning confocal microscopy, and extended over several micrometers. The gels were integrated as active layers in field-effect transistors, which provided good bulk electron and hole charge mobilities as well as light emission generation. The tetra-substituted pyrene derivative is not a gelator but displays a stable liquid crystalline phase with 2D hexagonal symmetry between 20 and 200 degrees C. The pronounced luminescence properties of the mesophase allow one to observe original mesophase textures with flower-like patterns directly by fluorescence microscopy without crossed-polarizers.

The synthesis, structural characterization, photoluminescence, and excited state absorption properties of a series of platinum(II) terpyridyl complexes bearing a bipyridyl acetylide subunit are presented. The [(t)Bu(3)tpyPtC identical withCbpy](+) (1) complex displays a broad and structureless emission profile at room temperature (RT), a lifetime of 5.8 mus, and transient absorption (TA) difference spectra characteristic of a charge transfer (CT) excited state. Upon coordination of Fe(2+) to 1, producing tetranuclear 2, the CT emission was quantitatively quenched presumably through the low-lying iron-based ligand field states present. Surprisingly, the addition of Zn(2+) to solutions of 1 produces a higher energy emissive state with a substantially longer excited state lifetime of 16.1 mus. The combined spectroscopic data measured for the zinc titration product (3) suggests that the overall excited state is dominated by a CT manifold, albeit at higher energy relative to 1. The photophysics of a bis-phosphine complex bearing two trans-disposed bpy-acetylide subunits (4) produced a model chromophore possessing an intraligand triplet excited state with a lifetime of 26 mus at RT. The bipyridyl analogue of 1, (t)Bu(2)bpyPt(C identical withCbpy)(2) (5), was also prepared and its photophysics are consistent with a lowest CT parentage at RT. The 77 K emission spectra measured for complexes 1, 3, 4, and 5 are all consistent with a triplet bpy-acetylide localized excited state; the E(00) energies vary over a modest 344 cm(-1) across the series. However, the shorter 77 K excited state lifetimes observed for 1, 3, and 5 in comparison to 4 suggests that the energetically proximate CT state in the former compounds significantly influences excited state decay at low temperature.

A hybrid [Pt((t)Bu(3)terpy)(C[triple bond]C-Ph-C(60))](+) complex (Pt-Fu) wherein a phosphorescent platinum center is linked to fullerene has been prepared using a copper(I)-promoted cross-coupling reaction. The electrochemical and spectroscopic properties were understood in light of the properties of the isolated building blocks and references compounds, Pt and Fu. In particular, in Pt-Fu, the electrochemical studies revealed that the first reduction process is fullerene-based and that the lowest-energy Pt(+)-Fu(-) charge-separated (CS) state lies in the range 2.0-2.1 eV. The luminescence properties of the investigated species have been monitored in a CH(2)Cl(2) solvent at room temperature and in a MeOH/EtOH (1:4 v/v) glassy solution at 77 K. Upon excitation at 450 nm at room temperature and in air-free solvent, Pt displays an intense luminescence of (3)MLCT nature, with lambda(max) = 605 nm (523 nm at 77 K, corresponding to 2.37 eV), phi(em) = 0.013, and tau(em) = 920 ns. Under the same conditions, Fu exhibits the typical (1)C(60) fluorescence, with lambda(max) = 708 nm (703 nm at 77 K, corresponding to 1.76 eV), phi(em) = 6.0 x 10(-4), and tau(em) = 1.2 ns. For Pt-Fu, room-temperature excitation at 450 nm yields Pt*- and Fu*-centered excited states in a 1.2:1 proportion. However, no Pt-based emission is observed, and (i) in an air-free solvent, (1)Fu fluorescence is observed, while (ii) in an air-equilibrated solvent, singlet oxygen sensitization by the (3)Fu level takes place. Very close (1)O(2)* fluorescence intensities are observed at 1278 nm for isoabsorbing solutions at 450 nm of Fu and Pt-Fu, consistent with complete Pt --> Fu energy transfer in the dyad. The room-temperature nanosecond transient absorption spectra for Pt-Fu and Fu exhibit peaks at 680 and 690 nm with tau(TA) = 14.3 and 24.8 micros, respectively; in both cases, these are attributed to absorption by the fullerene triplet. By contrast, no CS species, Pt(+)-Fu(-), are detected. The Pt --> Fu energy transfer is discussed, and the rate constant for the (3)Pt-Fu --> Pt-(1)Fu step is evaluated, k(en) > 10(7) s(-1).

Efficient photoinduced energy migration is obtained in a new star-shaped multichromophoric species made of three different Bodipy dyes and a truxene core.

The synthesis, structural characterization, and photoluminescence (PL) properties of the square-planar terpyridylplatinum(II) complex [ ( t )Bu 3tpyPtCCtpy] (+) ( 1) and the octahedral trinuclear Fe (II) and Zn (II) analogues [Fe( ( t )Bu 3tpyPtCCtpy) 2] (4+) ( 2) and [Zn( ( t )Bu 3tpyPtCCtpy) 2] (4+) ( 3) are described. The photophysical properties of the mononuclear Pt (II) complex 1 are consistent with a charge-transfer excited-state parentage producing a large Stokes shift with a concomitant broad, structureless emission profile. The Fe-based ligand-field states in 2 provide an efficient nonradiative deactivation pathway for excited-state decay, resulting in a nonemissive compound at room temperature. Interestingly, upon chelation of 1 with Zn (II), a higher energy charge-transfer emission with a low-energy shoulder and a 215 ns excited-state lifetime is produced in 3. A spectroscopically identical species relative to 3 was produced in control experiments when 1 was reacted with excess protons (HClO 4) as ascertained by UV-vis and static PL spectra measured at room temperature and 77 K. Therefore, the chelation of Zn (II) to 1 is acid-base in nature, and its Lewis acidity renders the highest occupied molecular orbital level in 1 much less electron-rich, which induces a blue shift in both the absorption and emission spectra. At 77 K, complexes 1, 3, and protonated 1 display at least one prevalent vibronic component in the emission profile (1360 cm (-1)) resembling PL emanating from a ligand-localized excited-state, indicating that these emitting states are inverted relative to room temperature. These results are qualitatively confirmed by the application of time-dependent theory using only the 1360 cm (-1) mode to reproduce the low-temperature emission spectra.

A new multicomponent species made of Pt(II) terpyridine and difluoroborondipyrromethene (bodipy) dyes is synthesized and its absorption, redox, and emission properties are reported; photoinduced energy transfer from the Pt-based (3)MLCT state to the bodipy triplet occurs both at room temperature and at 77 K.

Neutral orthometalated platinum(II) complexes of the deprotonated 6-phenyl-2,2'-bipyridine ligand (bearing a trialkoxygallate, tolyl, ethynyltrialkoxygallate, or ethynyltolyl substituent) and a sigma-bonded Cl, ethynyltolyl, or ethynyltrialkoxygallate coligand have been prepared by a stepwise procedure based on copper-promoted cross-coupling reactions. The X-ray structure of the [2-(p-tolyl)ethynyl][4-{2-(p-tolyl)ethynyl}-6-phenyl-2,2'-bipyridyl)]platinum(II) complex revealed a coplanar arrangement of all residues bound to platinum, although the tolylethynyl groups exhibit position-dependent bending in the solid state. The complexes exhibit charge-transfer absorption in the visible region. All except two of the complexes also exhibit charge-transfer emission, typically from an excited state that has a submicrosecond lifetime at room temperature in deoxygenated dichloromethane solution. In accordance with the presence of a carbometalated polypyridine ligand, the emitting state is assumed to have a mixture of metal-to-ligand charge-transfer (MLCT) and intra-ligand charge-transfer (ILCT) character. However, spectral comparisons and electrochemical data suggest that the emissive state also exhibits interligand charge-transfer (LLCT) character when an electron-rich ethynylaryl group is bound to platinum. In keeping with altered orbital parentage in the latter systems, the emission occurs at longer wavelength. The excited-state lifetime is also shorter, evidently due to vibronic interactions. The decay is so efficient when an ethynyltrialkoxygallate group binds to platinum that there is no detectable emission in fluid solution, although the complexes do emit in a frozen glass. The excited states are subject to associative (exciplex) quenching by Lewis bases, but the admixture of ILCT and/or LLCT character diminishes efficiency, except for relatively strong bases like dimethyl sulfoxide and dimethylformamide.

A generic design principle for the preparation of a variety of substituted phenyl-polypyridine ligands is described. These ligands are readily prepared by a regioselective [4+2] cycloaddition between electron-deficient dienes, such as 2,6-disubstituted-1,3,4-triazines, and ethynyl-arenes or ethynyl-alkanes. Exceptional reactivity is found with electron-rich dienophiles bearing ethynylgallate or ethynylphenyldibutylamino groups. Two regioisomers are formed, the meta being preferred due to favorable pi-pi interactions in the transition state, while the para isomers are formed in low yields in most cases. The use of tert-butylacetylene or N,N-dimethylamino-2-propyne, however, drives the reaction exclusively to the para isomer. Di-N,N-dibutylaminophenyl or isoquinoline ligands can also be produced in a single step by reverse Diels-Alder reactions. Cross-coupling reactions of iodo-substituted ligands or their platinum(II) complexes under Pd(0) catalysis gives branched ligands and complexes bearing paraffin chains, electron-donor or electron-acceptor groups. The use of a chloro-Pt(II) complex of an iodo-functionalized ligand allows both halogens to be replaced by ethynyl groups by using different catalysts. This methodology readily accommodates various functional groups and has been successfully extended to systems containing a variety of donor/acceptor frameworks. All ligands strongly absorb in the near-UV and luminesce in solution at rt with quantum yields ranging from 0 to 66%. Excited state lifetimes are in the nanosecond range and the solvent effects are in keeping with singlet excited states mixed with charge-transfer character. As deduced from spectroscopic and electrochemical studies, the di-n-butylamino derivatives are strong reductants in the excited state.

We report the preparation and characterization of dinuclear Pt-Ln complexes constructed from a square-planar Pt(II) core bearing an ethynyl-terpyridine residue connected to platinum by the ethynyl bond. Complexation of the neutral Eu(hfac)3 (hfac = hexafluoroacetylacetonate) fragment to free terpyridine (terpy) gives a stable bimetallic complex (log beta = 6.7). In the crystal structure, the flat Pt[triple bond]terpy core coordinates to Eu(III), which is nonacoordinated with the three nitrogen atoms of the terpy subunit and six oxygen atoms of the three hfac ligands. These atoms form a distorted monocapped square antiprism with a pseudo-C2 symmetry axis passing through the nitrogen atom of the central pyridine ring and the Eu atom. Spectroscopic measurements showed that irradiation with visible light of wavelength up to 460 nm in the 1MLCT state of the Pt subunit resulted in a quantitative energy transfer to the Eu center, which strongly luminesces in the red with an overall luminescence quantum yield of 38%. The energy-transfer process is quantitative and not sensitive to oxygen, and the complexation of Eu to the Pt metallosynthon allows the recovery of the energy lost due to triplet-oxygen quenching of the 3MLCT state observed in the uncomplexed Pt precursor.

Platinum(II) complexes bearing various alkyne-pyrene, alkyne-4'-terpyridine and alkyne-dibutoxyphenylacetylide-terpyridine units were constructed in a step-by-step procedure based on copper-promoted cross-coupling reactions with preconstructed modules; formation of bis(ligand) complexes of Fe(II) and Zn(II) by binding of the pendent terpyridine units provided heterotrinuclear derivatives, all of which exhibit highly structured absorption features in solution and display a rich electrochemistry due to the presence of various redox active modules.

The proteinaceous content of garlic (Allium sativum) was characterised according to its amino acid composition by using a gas chromatography-mass spectrometry (GC-MS) analytical procedure. The procedure was tested on fresh and aged garlic samples as well as on reference gilding specimens prepared according to old recipes. The proteinaceous pattern showed a characteristic distribution of amino acids with glutamic acid being the major component. The average amino acidic composition was: glutamic acid (Glu; 29%), aspartic acid (Asp; 17%), serine (Ser; 11%), alanine, glycine, valine, leucine, lysine and phenylalanine (Ala, Gly, Val, Leu, Lys and Phe; 5-6%), isoleucine, proline and tyrosine (Ile, Pro and Tyr; 2-3%), methionine and hydroxyproline (Met and Hyp; 0.5%). In order to distinguish this material from animal glue and egg, which are the other proteinaceous media commonly used in gilding techniques, a database of amino acid percentages of the three proteins was built up and submitted to principal component analysis. Three separate clusters were obtained, allowing the protein identification. The application of the procedure on several gilding samples from Italian wall and easel paintings (13th-17th century) permitted to evidence the use of garlic as a gluing agent.