A linear porphyrin-based tecton bearing two 4,4[Formula: see text]bipyridinium units (viologens) and two monomethyl-ether triethylene glycol-substituted phenyl substituents at the meso positions was synthesized and characterized. The latter was involved in the redox-triggered formation of linear supramolecular assemblies with cucurbit[8]uril (CB[8]) cavitands in aqueous media. The CB[8]-promoted intermolecular [Formula: see text]-dimerization of the viologen cation radicals introduced at the meso positions of the porphyrin platform has been brought to light through the diagnostic signatures of the 1:2 host-guest ternary caviplexes formed between viologen and CB[8] and by spectroscopic data collected after electrochemical reduction of the viologen-based tectons.

Viologen-based ditopic bis-pyridinyl-triazole bidentate ligands self-assemble in the presence of palladium ions into supramolecular polymers whose structure is imposed by the directed formation of coordination bonds. Light-irradiation of these electron-responsive supramolecular materials triggers a photo-induced electron transfer yielding isolated π-radicals and dimers of radicals. The photoreduction events and the associated dimerization steps trigger a large-scale reorganization occurring within the supramolecular network yielding aggregates or gels depending on the irradiation conditions (power, duration). Detailed electrochemical, spectro-electrochemical and photochemical analyses were conducted to understand the mechanisms at stakes in these light-induced aggregation and gelation.

Switchable compounds have been often described as promising candidates for electronic applications such as molecular-scale calculators. A step further is the combination of several different switchable molecules in larger functional macromolecules to design more sophisticated Boolean logic gates. Here, complex logic devices have been built via a redox- and photoactive metallopolymer based on dithienylethene-appended iron bis-terpyridine units. The commutation of individual building blocks of the metallopolymer is achieved using light or an electrical stimulus, thus demonstrating a way to build multiswitchable molecular logic gates by a rational chemical design. This functional material exhibits five accessible and distinguishable stable states that can be used as AND and OR logic gates, as a half-adder or multiplexer.

A metal-induced self-assembly strategy is used to promote the π-dimerization of viologen-based radicals at room temperature and in standard concentration ranges. Discrete box-shaped 2:2 (M:L) macrocycles or coordination polymers are formed in solution by self-assembly of a viologen-based ditopic ligand with cis-[Pd(en)(NO3)2], trans-[Pd(CH3CN)2(Cl)2], or [Pd(CH3CN)4(BF4)2]. Changing the redox state of the bipyridium units involved in the tectons, from their dicationic state to their radical cation state, results in a reversible "inflation/deflation" of the discrete 2:2 (M:L) macrocyclic assemblies associated to a large modification in the size of their inner cavity. Viologen-centered electron transfer is also used to trigger a dissociation of the coordination polymers formed with tetrakis(acetonitrile)Pd(II), the driving force of the disassembling process being the formation of discrete box-shaped 2:2 (M:L) assemblies stabilized by π-dimerization of both viologen cation radicals.

Photochromic dimethyldihydropyrenes substituted with electron-withdrawing pyridinium groups have shown an increase of photo-induced ring-opening efficiency and a light sensitivity that is red shifted relative to the unsubstituted compound. However, a recently synthesized tetrapyridinium derivative showed a considerable decrease of the photo-isomerization quantum yield relative to the monopyridinium and bispyridinium derivatives. We provide a rationale for this unexpected photochemical behavior based on the comparative theoretical investigations of the relevant excited states of these systems. In particular, we found that the nature and order of the lowest two excited states depend on the number of pyridinium groups and on the symmetry of the system. While the lowest S 1 excited state is photo-active in the monopyridinium and bispyridinium derivatives, the photo-isomerizing state is S 2 in the reference unsubstituted compound and both S 1 and S 2 lead to isomerization in the tetrapyridinium derivative, albeit with a low efficiency. In the latter derivative, the photo-isomerization is hindered by the particular S 1 /S 2 conical intersection topology.

Stimuli-responsive self-assembled molecular materials are currently subject to intense research activity. This growing interest stems largely from the myriad of exciting applications envisioned for dynamic supramolecular assemblies, also known as dynamers, in materials science, sensing, catalysis and electronics. Enormous technologic interests are for instance at stake in being able to devise molecular objects that could respond to external stimuli by changes in structure and function. These particular properties can lead to applications in various domains as (i) in molecular electronics, (ii) in analytic science, with switchable hosts allowing the controlled binding/release of pollutants or drugs, (iii) in materials science with the development of adaptive supramolecular polymers. Our group has been focusing over the past few years on the development of tailor-made redox-controllable molecular and supramolecular systems involving electrogenerated pi-radicals as key responsive and/or assembling elements [1, 2]. In this lecture, we will focus on the physico-chemical properties of a series of porphyrin-based molecular tectons whose self-assembly can be controlled with optical or electrical stimulus. The dynamic properties of these stimuli-responsive molecular architectures and molecular materials will mainly be discussed on the basis of electrochemical, spectroelectrochemical and ESR experiments supported by quantum chemical calculations [3-6]. References : [1] C. Kahlfuss, E. Saint-Aman, C. Bucher (2016). Redox-controlled intramolecular motions triggered by π-dimerization and πmerization processes In T. Nishinaga (Ed.), Organic Redox Systems: Synthesis, Properties, and Applications (pp. 39). New-York: John Wiley and sons. [2] H. D. Correia, S. Chowdhury, A. P. Ramos, L. Guy, G. J.-F. Demets, C. Bucher, Polymer International 68 , 572 (2019). [3] S. Chowdhury, Y. Nassar, L. Guy, D. Frath, F. Chevallier, E. Dumont, A. P. Ramos, G. J.-F. Demets, C. Bucher, Electrochimica Acta 316 , 79 (2019). [4] C. Kahlfuss, S. Denis-Quanquin, N. Calin, E. Dumont, M. Garavelli, G. Royal, S. Cobo, E. Saint-Aman, C. Bucher, Journal of the American Chemical Society 138 , 15234−15242 (2016). [5] C. Kahlfuss, T. Gibaud, S. Denis-Quanquin, S. Chowdhury, G. Royal, F. Chevallier, E. Saint-Aman, C. Bucher, Chemistry - A European Journal 24 , 13009 (2018). [6] C. Kahlfuss, R. Gruber, E. Dumont, G. Royal, F. Chevallier, E. Saint-Aman, C. Bucher, Chemistry - A European Journal 25 , 1573 (2019). Figure 1

Two photoswitchable compounds that can operate under visible light irradiation are prepared and investigated using spectroscopic and computational studies. These all-visible systems are based on the dimethyldihydropyrene (DHP)/cyclophanediene (CPD) photochromic couple connected either to a bipyridine (bpy) unit or to a (tris(bpy)ruthenium(II)) complex through a pyridinium bridge. In these compounds, the DHP to CPD isomerization and the reverse CPD to DHP conversion can be triggered by illumination with red (>630 nm) and blue (460 nm) lights, respectively. The unambiguous and reversible response of these systems triggered by visible light make them potential candidates for biological purposes and electronic devices.

A new material of magnesium(II) polymer compound with the formula {[Mg-II(TPP)(pz)](center dot)0.5[Mg-II(TPP)](CH2Cl2)-C-center dot}(n) (I), (TPP) = meso-tetraphenylporphyrinato and pz = pyrazine) was synthetized and characterized by IR, UV-visible, PL photoluminescence and H-1 NMR spectroscopy studies, single-crystal XRD analyses and cyclic voltammetry. The crystal structure of (I) is made by the 1D {[Mg(TPP)(pz)]} polymeric chains (molecules I(A)) where the tetracoordinated magnesium(II) complexes [Mg(TPP)] (molecules I(B)) are located as well as the dichloromethane solvent molecules. The crystal packing of (I) is stabilized by intermolecular C-H center dot center dot center dot Cg pi interactions where Cg is the centroid of phenyl and pyrrole rings. Additionally, the photophysical properties have been evaluated by UV-visible absorption and fluorescence emission spectroscopies. The UV-visible spectrum of (I) shows a redshift Soret band value (428 nm) compared to that of the free base H2TPP porphyrin while the lambda(max) values of the Q bands are in the range 560 - 610 nm. The optical gap of (I) was estimated at 1.99 eV. The cyclic voltammogram of the title compound presents two reversible oxidation waves and one reversible reduction wave. The HOMO and LUMO energy values were deduced from the voltammogram which are -4.96 and -2.85 eV respectively. Furthermore, bioactivity investigations revealed that the free porphyrin, the starting material [Mg-II(TPP)] and complex (I) could be used as potential antibacterial agents. (C) 2020 Elsevier B.V. All rights reserved.

This work focuses on new materials based on the addition of zinc as specifically metal centers for the capture of NO2 gas with DFT calculations. This study aims at the synthesis and the spectroscopic characterizations of the free base meso-tetrakis-,(3,4,5trimethoxyphenyl) porphyrin (H2TTMP) (I), meso tetrakis(3,4,5trimethoxyphenyl) porphyrinato) zinc(II) complex [Zn(TTMP)] (II) and the (4-cyanopyridine) meso-tetrakis - (3,4,5-trimethoxyphenyl) porphyrinato) zinc(II) [Zn(TTMP)(4-CNpy)] (III). X-ray molecular structure of (III) displays that the crystal lattice of the five-coordinated zinc( II) coordination compound, is made up of two dimensional layers parallel to the [0 0 1] direction sustained by C-H center dot center dot center dot Cg and Cg center dot center dot center dot Cg pi inter and intra-molecular interactions. Notably, the presence of voids of 1.2 angstrom and a grid of 0.7 angstrom are located between the 2D layers. DFT calculations on the three porphyrin derivatives were carried out and results indicated an agreement with both IR and UV-vis experimental data. The adsorption behaviors of the toxic NO2 gas molecules on the porphyrin derivatives were investigated using first-principles density functional theory. Based on the MEP of (I)-(III) molecules and the MEP of NO2 and the calculation of the adsorption energies, we suggest that compound (II) has the best attraction. More importantly, after NO2 chemi-sorption on porphyrin derivatives, a remarkable red-shift is observed in the optical spectra, especially for II/NO2 complex, thus offering a good index to detect the binding of NO2. The optical spectra can therefore be used to detect the presence of NO2 and porphyrin derivatives indicate appropriate properties to establish good NO2 sensors.

In this paper we reported on the spectroscopic, physicochemical and the catalytic properties of dichloride (5,10,15,20-tetraphenylporphyrinato)antimony(V) hexachloridoantimonate(V) [Sb(TPP)Cl-2] SbCl6(2). Optical spectroscopy data showed a red-shift of both absorption bands; the Soret and the Q, which was observed of the antimony complex compared with that free base porphyrin H2TPP. The optical gap E-g.op was calculated using the Tauc plot method suggesting a semi-conductor product. The [Sb(TPP)](+) and the [Sb(TPP)Cl-2](+) fragments were determined using the mass spectrometry. The fluorescence investigation showed a high fluorescence quantum yield with a lifetime of (2) compared to the free base porphyrin.32% of the calmagite solution was removed (C-0 = 40 mg/L, pH = 6, mass = 3 mg) using (1). However, using the system (2)H2O2 (C-0 = 40 mg/L, pH = 6, t = 240 mins), the yield value of decolourisation was found to be 94% at equilibrium.

We have developed a strategy enabling control over the organization of ditopic molecular tectons within a palladium-based self-assembled system. The key electron-responsive sub-unit is a viologen-based mechanical hinge that can toggle under electric stimulation between a folded and a stretched position, the driving force of the folding motion being the π-dimerisation of the electrogenerated viologen cation radicals. The title ditopic tecton features two planar, N2-type, triazole/pyridine-based bidentate binding units, providing the tecton with the ability to chelate two palladium ions both in its folded and in its elongated conformations. Association of this ditopic redox-responsive tecton with palladium to form 1D self-assembled architectures undergoing large scale reorganizations in solution under electric stimulation, has been established on the ground of spectroscopic, electrochemical, spectro-electrochemical and rheological data. Our result reveal that addition of metal leads to a significant stabilization of the π-dimer species in solution and that the redox-triggered reorganisation of the tectons comes along in suitable conditions with a macroscopic sol/gel-type phase transition.

Poly-zinc-octaethylporphyrin/P5W30 films have been obtained through incorporation of Preyssler-type polyoxometalate ions, namely [NaP5W30O110]14- (P5W30) into zinc octaethylporphyrin/viologen-based polymers (poly-ZnOEP) films. The latter has been achieved through a metathesis reaction involving exchange of the initial counter ions (PF6−) of the positively charged poly-ZnOEP by P5W30. The investigated polymers involve ZnOEP units covalently linked either through a dicationic mono-viologen or through a tetracationic bis-viologen spacer. These copolymers have been characterized by UV/Vis absorption spectroscopy, X-ray photoelectron spectroscopy, electrochemistry, AFM and by electrochemical impedance spectroscopy. Formation of the polymers through electropolymerization of viologen and porphyrin building blocks has also been monitored by EQCM. QCM measurements have been carried out to study the exchange of PF6− by [NaP5W30O110]14−. Finally, the photovoltaic performances of these polymers have been assessed by photocurrent transient measurements carried out under visible illumination.

A dynamic supramolecular approach is developed to promote the π-dimerization of viologen radicals at room temperature and in standard concentration ranges. The approach involves cis- or trans-protected palladium centers serving as inorganic hinges linking two functionalized viologens endowed with metal-ion coordinating properties. Based on detailed spectroscopic, electrochemical and computational data, we show that the one-electron electrochemical reduction of the viologen units in different dynamic metal/ligand mixtures leads to the formation of the same intramolecular π-dimer, regardless of the initial environment around the metallic precursor and of the relative ratio between metal and ligand initially introduced in solution. The large-scale electron-triggered reorganization of the building blocks introduced in solution thus involves drastic changes in the stoichiometry and stereochemistry of the palladium/viologen complexes proceeding in some cases through a palladium centered trans→cis isomerization of the coordinated ligands.

Laboratory of Physico-Chemical of Mate University of Monastir, 5000 Monastir, Tun Textile Materials and Process Research U Monastir, Tunisia Department of Molecular Chemical, UMR C Inorganic Chemistry, University J. Fourier, R Grenoble Cedex 9, France Chemistry Department, King Fahd Univer 31261, Saudi Arabia. E-mail: tawk@kfupm Department of Molecular Chemicals (C domaine Universitaire, 301 rue de la ch 40700, 38058 Grenoble CEDEX 9, France † Electronic supplementary information ( 10.1039/c8ra01134f Cite this: RSC Adv., 2018, 8, 20143

We report the study of stimuli-responsive ZnII and FeII coordination polymers (MC34+ or MC24+ with M=Fe2+ or Zn2+ ). These soluble metallopolymers were formed spontaneously by reaction of an organic ligand (C34+ or C24+ ) with one molar equivalent of metal ions. The C34+ and C24+ ligands incorporate two chelating terpyridine groups bridged by a redox responsive hinge featuring two viologen units (viologen=N,N'-dialkyl-4,4'-bipyridinium) linked either with propyl (C34+ ) or ethyl (C24+ ) chains. The viologen units in the polymer chains were reduced (1 e- per viologen group) either by bulk electrolysis or by visible-light irradiation carried out in the presence of a photosensitizer. The 1 e- reduction of the viologen units in the MC24+ polymers induced a slight decrease in the viscosity of the solutions due to a modification of the overall charge carried by the metallopolymers. In strong contrast, reduction of coordination polymers involving propyl linkers (MC34+ ) led to a remarkable increase (≈+400 %) in observed viscosity. This reversible effect was attributed to a folding of the polymer chains triggered by π-dimerization of the photo-generated viologen cation radicals.

This work reports on the synthesis and characterization of a new porphyrins complex:[Zn(TEBOP)(4,4-bpy)](4,4-bipyridine)(5,10,15,20-(tetraethyl-4(4-butyryl)oxyphenyl)porphyrinato)zinc(ii) (3). Single crystal X-ray diffraction, photophysical and electrochemical characteristics were studied. The prepared complex, penta-coordinated zinc(ii) porphyrin derivatives shows moderate ruffling distortion and the zinc atom is nearly planar with the porphyrin core. Tolyl and ethyl-4(4-butyryl)oxyphenyl) moieties at the meso positions present a bathochromic shift of the absorption bands, and a notable increase in the absorption coefficient of the Q(0,0) and Q(0,1) bands was observed with a higher fluorescence quantum yield and lifetime compared with the free base porphyrin. The electrochemical investigation shows a reversible reduction of the synthesized complexes. The catalytic power and the adsorption properties of the prepared complexes were studied for Calmagite degradation, an azoic organic dye. The results reveal that the studied compounds could be used as catalysts for the decolourisation of dyes in the presence of H2O2.