Alessio Orbelli Biroli

Italian National Research Council | CNR · Institute of Molecular Science and Technologies ISTM

The presence of a liquid electrolyte in dye-sensitized solar cells (DSSCs) is known to limit the time stability of these devices due to leakage and evaporation phenomena. To overcome this issue, gel-state electrolytes may represent a good solution in order to maintain stability and good performances, albeit at lower costs. In the present work, two...

Electron donor–acceptor (EDA) complexes are characterized by charge-transfer (CT) processes between electron-rich and electron-poor counterparts, typically resulting in a new absorption band at a higher wavelength. In this paper, we report a series of novel 2,6-di(imino)pyridine ligands with different electron-rich aromatic substituents and their 1...

Stabilizing ordered assemblies of molecules represents the first step towards the construction of molecular devices featuring hybrid (organic-inorganic) interfaces where molecules can be easily functionalized in view of specific applications. Molecular layers of planar metal-tetraphenylporphyrins (MTPP) grown on an ultrathin iron oxide [namely Fe(0...

Hybrid sp-sp2 structures can be efficiently obtained on metal substrates via on-surface synthesis. The choice of both the precursor and the substrate impacts on the effectiveness of the process and the stability of the formed structures. Here we demonstrate that using anthracene-based precursor molecules on Au(111) the formation of polymers hosting...

Copper(II) azacyclam complexes (azacyclam = 1,3,5,8,12-pentaazacyclotetradecane) containing naphthyl or dansyl subunits can be prepared by template synthesis involving proper sulfonamide derivatives as locking fragments. The macrocyclic complexes are very poorly emissive due to the fluorescence-quenching behavior displayed by Cu2+ ions. However, th...

In this paper we report an investigation on the linear and nonlinear properties of a non-classic push-pull molecule, based on the molecular design concept of a ‘donor-free’ chromophore. Herein a terthiophene unit acts both as a donor and a π-spacer group and a tris(trimethylsiloxy)silane substituent as an acceptor group. This latter can represent a...

We have recently discussed how organic nanocrystal dissolution appears in different morphologies and the role of the solution pH in the crystal detriment process. We also highlighted the role of the local molecular chemistry in porphyrin nanocrystals having comparable structures: in water‐based acid solutions, protonation of free‐base porphyrin mol...

The desirable self‐assembly (SA) of repeated 2D stacked layers requires a “holistic analysis” of three interconnected components: the electrode, the interface, and the molecular component; among them, the contact interface bears the largest burden responsibilities. Epitaxial growth (EG) of coherent 2D+n stacked heterojunction by solvent‐free deposi...

In article number 2011008, Alberto Bossi, Gianlorenzo Bussetti, and co‐workers present a coherent layered film grown on an archetypal Fe metal electrode. The ingredients for the controlled in‐vacuum self assembly are chemical decoupling of the contact interface, lateral (2D) ordering of the molecules, rigid molecule‐to‐molecule coupling along the t...

Two novel phenothiazin-5-ium derivatives bearing cyclam moieties ( 3a + and 3b + ) were synthesized and investigated as Cu 2+ sensors. Both ligands show intense spectral changes in the presence of Cu 2+ in aqueous solutions. The high molar extinction coefficient of the chromophore allows both naked eye detection and spectrophotometric quantitative...

Two 4-styrylpyridines with a –NO2 (L1) or –NMe2 (L2) group were axially coordinated to A4 ZnII porphyrins displaying in 5,10,15,20 meso position aryl moieties with remarkable electron withdrawing properties or with moderate to strong electron donor properties. The second order NLO properties of the resulting complexes were measured in solution usin...

In this research, two 4-styrylpyridines carrying an acceptor –NO2 (L1) or a donor –NMe2 group (L2) were axially coordinated to A4 ZnII porphyrins displaying in 5,10,15,20 meso position aryl moieties with remarkable electron withdrawing properties (pentafluorophenyl (TFP)), and with moderate to strong electron donor properties (phenyl (TPP) < 3,5-di...

In situ atomic force microscopy (AFM) measures, with the scanner head immersed inside a liquid (namely an electrolyte), are—generally speaking—not easy to be acquired in real time, i.e., during electrochemical processes, the immersion of a massive and wide system (with respect to the electrochemical cell mean radius) can significantly perturb the e...

Controlling the molecular arrangement of properly designed materials is the ultimate target of studies in surface protection by organic thin films. The properties of the films are even more critical when the protection ability must be match with the function of the underneath active surface as in the case of electrodes covered by suitable protectiv...

We investigated the impact of Singly Occupied Molecular Orbital (SOMO) energy on the n-doping efficiency of benzimidazole-derivatives. By designing and synthesizing a series of new air-stable benzimidazole-based dopants with different SOMO energy levels, we demonstrated that an increase of the dopant SOMO energy by only ~0.3 eV enhances the electri...

Three perfluorinated ZnII porphyrins were evaluated as n-type sensitizers in photoelectrosynthetic cells for HBr and water splitting. All the dyes are featured by the presence of pentafluorophenyl electron withdrawing groups to increase the ground state oxidation potential and differ for the nature and the position of the π-conjugate linker between...

Two different high potential Zn(II) porphyrin designs carrying either 4 or 5 meso pentafluorophenyl moieties as electron acceptor groups and a further electron withdrawing branch inserted in either the β (1) or meso (2) position were tested in photoelectrosynthetic cells for HBr splitting. Photoaction spectra in the presence of HBr showed that red...

Dye-Sensitized Solar Cells (DSSCs) are a highly promising alternative to conventional photovoltaic silicon-based devices, due to the potential low cost and the interesting conversion efficiencies. A key-role is played by the dye, and porphyrin sensitizers have drawn great interest because of their excellent light harvesting properties mimicking pho...

Chiral electroanalysis could be regarded as the highest recognition degree in electrochemical sensing, implying the ability to discriminate between specular images of an electroactive molecule, particularly in terms of significant peak potential difference. A groundbreaking strategy was recently proposed, based on the use of "inherently chiral" mol...

This short review outlines the main results obtained by our research group over the last 15 years in the field of porphyrins and metal porphyrins for second order nonlinear optics (NLO). This overview aims to provide a general framework of the key factors which affect the second order NLO response of porphyrin chromophores. The pivotal role of the...

The complex [Pt(i‐Pr2pipdt)(Quinoxdt)] (i‐Pr2pipdt = 1,4‐di‐isopropyl‐piperazine‐2,3‐dithione; Quinoxdt= [1,4]dithiino[2,3‐b]quinoxaline‐2,3‐dithiolate) exhibits a remarkable green emission at 550 nm (room temperature), which is above the lowest excited state. The complex is characterized by negative solvatochromism as well as a high second‐order p...

The development of building integrated photovoltaic (BIPV) technology and its implementation in construction of the building envelop provide aesthetical, economical and technical solutions toward the zero-energy building. In this perspective dye-sensitized solar cells (DSSCs), which can be obtained in transparent form and with tunable different col...

Organic molecules have been proposed as promising candidates for electrode protection in acidic electrolytes. The use of tetraphenyl-porphines (H2TPP) as graphite surface-protecting agents in sulphuric acid (H2SO4) is one of the newest. With the aim of unveiling the mechanism of such a protective effect, in this paper we test the stability of a H2T...

The combination of β-substituted Zn²⁺ porphyrin dyes and copper-based electrolytes represents a novel route for economic and environmentally friendly dye-sensitized solar cells. The new copper electrolyte, [Cu(2-mesityl-1,10-phenanthroline)2]+/2+, exceeds the performance reached by Co2+/3+ and I⁻/I3⁻ reference electrolytes.

Transient optical studies, at the nanosecond and femtosecond timescales, have been carried out on three structurally different porphyrin dyes to probe their charge transfer dynamics relevant to spectral sensitization and DSSC operation. Two of them, showing a β substitution pattern, were previously reported: ZnB bearing an ethynylphenyl cyanoacryli...

A series of 5,15 push-pull meso-diarylzinc(II) porphyrinates, carrying one or two -COOH or -COOCH3 acceptor groups and a -OCH3 or a -N(CH3)2 donor group, show in N,N-dimethylformamide and CHCl3 solutions a negative and solvent-dependent second-order nonlinear-optical (NLO) response measured by the electric-field-induced second-harmonic generation (...

Two novel green β-substituted Zn(II)-porphyrins, G1 and G2, based on a 4D-π-1A type substitution pattern have been synthesized. Their enhanced push-pull character, by reduction of H-L energy gaps, promotes broadening and red-shifting of absorption bands. The effective synthetic pathway and the remarkable spectroscopic properties make G2 ideal for B...

A series of new N-arylated ferrocenepyrazole structures, carrying different donor or acceptor substituents in the para position of the aryl ring, has been synthesized by the Chan–Lam cross-coupling reaction. The nonplanar geometric molecular structure of some of these chromophores together with their crystal packing was determined by X-ray diffract...

The introduction of alkoxy chains in the molecular architecture of meso push-pull porphyrins is of paramount importance aiming at high performing dye-sensitized solar cells (DSSCs) based on these specific sensitizers. Recently, we have demonstrated that the same approach is fruitful even if it is applied to tetraarylporphyrins with an acceptor/anch...

The common trend in designing dyes for use in DSSCs with iodide-based electrolyte is based on a donor–p spacer–acceptor (D–p–A) architecture. Here, we report two ‘donor-free’ cyanoacrylic end-functionalized oligo(3-hexylthiophene) dyes (5T and 6T). Despite having no donor group, both dyes show reversible first oxidation process. Both 5T and 6T have...

Pd nanoparticles within a nitrogen-containing covalent triazine framework (CTF) material are investigated to understand if the highly tunable CTF chemistry mediates the catalytic properties of the Pd nanoparticles. Surprisingly, our results demonstrate that the CTF stabilizes the formation of 2.6 nm PdHx particles within the pores. These confined P...

The antipodal introduction of two bromine atoms on 2,12 beta-pyrrolic position of 5,10,15,20-tetra(3,5-di-tert-butylphenyl)porphyrin was successfully achieved by a light-induced reaction of the substrate with excess NBS. Complexation with NiII of the major regioisomer led to good quality crystals, suitable for X-ray structure determination with unp...

Three new β-substituted ZnII -tetraarylporphyrinate dyes (1-3), bearing octyloxy chains at the o,o-, o,p- or o-positions of the four phenyl groups respectively, were synthesized, characterized and investigated as sensitizers for DSSCs. In particular, the alkoxy group position strongly influences their electronic absorption and electrochemical featu...

Time-resolved photophysical, and photoelectrochemical investigations have been carried out to compare the electron transfer dynamics of a 2-β-substituted tetraarylporphyrinic dye (ZnB) and a 5,15-meso-disubstituted diarylporphyrinic one (ZnM) at the electrolyte/Dye/TiO</sub>2 interface in PSSCs. Although the meso push-pull structural arrangement ha...

Three novel dyes based on ZnII porphyrinates combined, in β-pyrrolic position, with the π unit dithienylethylene (DTE) have been synthesized and investigated for application in DSSCs. The panchromatic effect due to elongation of the π-delocalized system through a bridge between the porphyrinic ring and the DTE unit such as the 4-ethynylstyryl (1),...

A facile and fast approach, based on microwave-enhanced Sonogashira coupling, has been employed to obtain in good yields both mono- and, for the first time, disubstituted push-pull Zn(II) porphyrinates bearing a variety of ethynylphenyl moieties at the β-pyrrolic position(s). Furthermore, a comparative experimental, electrochemical, and theoretical...

Push–pull Zn(II)-porphyrinates have recently shown attracting performances as light harvesting systems in dye-sensitized solar cells (DSSCs). To fully exploit their intrinsically high efficiency it is important to finely tune their HOMO and LUMO levels, which can be achieved by proper choice of the push and pull substituents. Of course such target-...

A multitechnique physicochemical comparative investigation involving TDDFT theoretical calculations, steady-state and time-resolved electronic absorption spectra, and electrochemical and photoelectrochemical investigations was carried out on a family of push–pull porphyrinic sensitizers ([5-(4′-carboxy-phenylethynyl)-15-(4″-methoxy-phenylethynyl)-1...

In this work, the second harmonic generation (SHG) and the nonlinear optical (NLO) coefficients d33 of PMMA films, containing 4 wt % NLO active macrocyclic chromophores based on a cyclotetrasiloxane scaffold and of their monomeric structurally homologous NLO active chromophores, were obtained by an electrical poling process and measured at room tem...

In this work we report some examples of fluorinated lanthanide complexes, in which the geometry of the coordination sphere is controlled by C–F···π system strong interactions involving the fluorinated ligands. Moreover we have also shown that a perfluorinated ligand, such as tris(pentafluorophenyl)phosphine oxide may have a role in increasing the p...

The synthesis and catalytic activity of some new titanium(IV) complexes with incompletely condensed Cy6Si6O7(OH)4 and endo-Cy8Si8O11(OH)2 (Cy = c-C6H11) silsesquioxane cages have been carried out with the aim of investigating new Ti silsesquioxane frameworks as molecular models of titanium active sites of catalysts prepared by grafting Ti(IV) precu...

Excimer formation in a new class of terthiophene-based fluorophores covalently bonded to a cyclotetrasiloxane scaffold has been demonstrated and the photophysical process ruling it has been investigated in detail and modeled theoretically. In contrast to the conventional systems in which long-living fluorophores such as pyrene are linked in the sam...

This work has produced experimental and theoretical evidence for the independence, on the nature of the metal, of the second order NLO response of [5-[[4′-(dimethylamino)phenyl]ethynyl]-15-[(4′′-nitrophenyl)ethynyl]-10,20-diphenylporphyrinate]M(II) NLO chromophores (M = Zn, Ni). EFISH measurements, carried out at a nonresonant 1.907 μm incident wav...

In this paper we report the synthesis, the photophysical, conductometric, and second-order nonlinear optical (NLO) characterization of an ensamble of four NLO active organic tails nanoorganized on a cyclotetrasiloxane ring, to produce various macrocyclic NLO chromophores. The second-order NLO response of the macrocyclic NLO chromophores measured by...

The synthesis and characterization of novel fluorinated Er3+ complexes emitting at the telecommunications wavelengths are presented. These new knowledge-based materials have been designed and optimized on the basis of an extensive photophysical investigation on the processes controlling the overall quantum yield, namely (i) the energy transfer proc...

We report time-dependent (TD) and coupled-perturbed (CP) DFT/HF investigations, on the linear and non-linear optical properties of M(II)-complexes of [5-[(4′-dimethylaminophenyl)-ethynyl]-15-[(4″-nitrophenyl)ethynyl]-10,20-diphenylporphyrin], with M=Zn, Cu, Ni. The TD-DFT absorption spectrum is in good agreement with the experimental one, allowing...

A series of sodium arylcyclotetrasiloxanolates properly functionalized in the para position of the aromatic ring, like [4-RC6H4Si(O)ONa]4 and the corresponding (trimethylsiloxy)cyclotetrasiloxanes [4-RC6H4Si(O)OSiMe3]4 (R=Cl, Br, CHCH2, CH2Cl), were prepared as scaffolds for anchoring second order NLO active or fluorescent organic chromophores. Suc...

Barium ion can be revealed at the micromolar concentration level by the blue-green fluorescence which arises upon the self-assembling process involving the metal ion and a novel bis-15-crown-5-naphthalenediimide derivative.

Ligands 2–5, containing the light-emitting subunit 1,8-naphthalimide, have been prepared and their photophysical properties studied by absorption and emission spectroscopy. Ligand 2 interacts in solution with several cations according to a 1 ∶ 2 (metal ∶ ligand) stoichiometry, the 1 ∶ 3 species being not favoured probably because of steric hindranc...

The new quadridentate bischelating ligands 2 and 3 display in solution the typical absorption and emission properties expected for naphthalenediimide derivatives. Spectrophotometric studies show that systems 2 and 3 interact with Zn(II), Cd(II) and Cu(I) in CHCl3 or MeCN according to an apparent 1:1 stoichiometry. Molecular modelling, ESI-MS and 1H...