Gennaro Pescitelli

• Prof., PhD
• Professor (Associate) at University of Pisa

Highly concentrated solutions of asymmetric semiconductor magic-sized clusters (MSCs) of cadmium sulfide, cadmium selenide, and cadmium telluride were directed through a controlled drying meniscus front, resulting in the formation of chiral MSC assemblies. This process aligned their transition dipole moments and produced chiroptic films with except...

The development of chiral organic materials with strong non-reciprocal chiroptical features may have major implications for cutting-edge technological applications. In this work, a new ad hoc synthesized chiral 1,4-diketo-3,6-dithienylpyrrolo[3,4-c]pyrrole dye,...

In this study, four depsides were isolated from Origanum dictamnus L. and Satureja pilosa Velen. medicinal plants and their structures were assessed by means of one‐dimensional (1D)‐ and two‐dimensional (2D)‐nuclear magnetic resonance, high resolution mass spectrometry, and electronic circular dichroism analyses. The compound 1 , herein reported fo...

S )‐Indoline‐2‐carboxylic acid (H‐(2 S )‐Ind‐OH) possesses the ability to influence the conformation of peptide bonds towards the cis amide isomer in polar solvents. However, its potential utilization as a conformational switch within long peptide sequences poses challenges due to its low reactivity and strong inclination to form diketopiperazines....

Phenyl‐4‐pyridyl‐2,5‐dipyrimidinylmethane (1) has been synthesized in five steps from 5‐methylpyrimidine. The structural feature of 1 is the symmetry elements with respect to the 180° rotation of the aryl group along the central C−C bonds. Due to this structural feature, the compound 1 is expected the good crystallinity despite of the asymmetric mo...

In the context of chiral π‐conjugated materials, the use of enantiopure alkylthio appendages represents a valid alternative to conventional alkoxy groups: sulphur atom is bigger and more electron‐rich than oxygen, thus allowing for higher polarizability, greater flexibility, larger bulkiness and lower structural anisotropy. In light of these consid...

Circularly polarized luminescence (CPL) from chiral molecules is attracting much attention due to its potential use in optical materials. However, formulation of CPL emitters as molecular solids typically deteriorates photophysical properties in the aggregated state leading to quenching and unpredictable changes in CPL behavior impeding materials d...

Magnetic circularly polarized luminescence (MCPL), i.e. the possibility of generating circularly polarized luminescence in the presence of a magnetic field in achiral or racemic compounds, is a technique of rising interest. Here we show that the far-red spin–flip (SF) transitions of a molecular Cr(iii) complex give intense MCD (magnetic circular di...

Hydantoins, a class of five-membered heterocyclic compounds, exhibit diverse biological activities. The aim of this study was to synthesize and characterize a series of novel 3,5-disubstituted hydantoins and to investigate their antiproliferative activity against human cancer cell lines. The new hydantoin derivatives 5a‒i were prepared as racemic m...

Circularly polarized luminescence (CPL) from chrial molecules is attracting much attention due to its potential in optical materials. However, formulation of CPL emitters as molecular solids typically deteriorates photophysical properties in the aggregated state leading to quenching and unpredictable changes in CPL behavior impeding materials devel...

Four families of structurally related chiral π‐conjugated oligomers bearing a hydroquinone (HQ), 1,5‐dihydroxynaphthalene (Naph), benzo[1,2‐b:4,5‐b’]dithiophene‐4,8‐diol (BDT) or 9H‐carbazole (CBZ) central core, for a total of 11 new compounds, have been synthesized by simple and versatile synthetic strategies involving Pd‐catalyzed cross‐coupling...

Engineering asymmetric transmission between left-handed and right-handed circularly polarized light in planar Fabry–Pérot (FP) microcavities would enable a variety of chiral light-matter phenomena, with applications in spintronics, polaritonics, and chiral lasing. Such symmetry breaking, however, generally requires Faraday rotators or nanofabricate...

According to the theoretical model based on the Mueller matrix approach, the experimental electronic circular dichroism (ECD) for thin films of chiral organic dyes can be expressed as the sum of several contributions, two of which are the most significant: 1) an intrinsic component (CDiso) invariant upon sample orientation, reflecting the molecular...

In this work, we synthesized a family of three structurally related chiral oligothiophenes containing a 1,4-diketo-3,6-diarylpyrrolo[3,4-c]pyrrole (DPP) unit as the central core; functionalized with the same (S)-3,7-dimethyl-1-octyl chains on the nitrogen atoms of lactam moieties, they only differ in the number of lateral thiophene units. The aggre...

We report the synthesis and characterization of four similar chiral 1-methyl-1H-imidazole π-conjugated derivatives. In particular, we focus on the thin film chiroptical characterization (electronic circular dichroism and circular polarized luminescence),...

Chiral materials formed by aggregated organic compounds play a fundamental role in chiral optoelectronics, photonics and spintronics. Nonetheless, a precise understanding of the molecular interactions involved remains an open problem. Here we introduce magnetic circular dichroism (MCD) as a new tool to elucidate molecular interactions and structura...

Chiral materials formed by aggregated organic compounds play a fundamental role in chiral optoelectronics, photo‐ and spin‐tronics. Nonetheless, a precise understanding of the molecular interactions involved remains an open problem. Here we introduce magnetic circular dichroism (MCD) as a new tool to elucidate molecular interactions and structural...

Chiroptical materials are gaining increasing interest due to their innovative character and their applications in optoelectronics and data encryption technologies. Fully harnessing the potential of building blocks from the “chiral pool”, such as native cyclodextrins (CDs), as they often lack chromophores suitable for the construction of materials w...

Instrumental techniques able to identify and structurally characterize the aggregation states in thin films of chiral organic π‐conjugated materials, from the first‐order supramolecular arrangement up to the microscopic and mesoscopic scale, are very helpful for clarifying structure‐property relationships. Chiroptical imaging is currently gaining a...

Hydrogen bonding greatly influences rates and equilibrium positions of chemical reactions, conformations, and sometimes even stereochemistry. This study reports on tetranitrofluorenone oximate, a novel dye capable of naked‐eye detection of hydrogen‐bond donating species (HBDs) and of rapid determination of H‐bond donation strength by hypsochromic s...

Achiral purely organic molecules can show selectivity towards circularly polarized light in emission in the presence of a magnetic field. This phenomenon is called magnetic circularly polarized luminescence (MCPL). Recently a few examples of MCPL from organic molecules have appeared in the literature. Through this technique, interesting photophysic...

Any device based on circularly polarized light (CPL)-emitting materials requires a high degree of circular polarization, quantified through the dissimmetry factor glum and related quantities such as the CPL brightness. However, maximizing |glum| is not an easy task. For a given chiral scaffold, for example helicenes, glum is usually confined below...

Chiral fluorescent macrocycles consisting of two to four units of dimethyl 2,5‐diaminoterephthalate can be readily synthesized in a one‐pot manner from inexpensive building blocks. Depending on the concentration, either a paracyclophane‐like dimer with closely stacked benzene rings or a triangular trimer is the main product of the reaction. The mac...

Invited for the cover of this issue are the research groups of Lorenzo Di Bari at the University of Pisa and Gianluca Maria Farinola at the University of Bari Aldo Moro. The image depicts three diketopyrrolo[3,4‐c]pyrrole–1,2,3‐1H‐triazole dyes with the same chiral appendage R* but different achiral substituent groups Y showing profoundly different...

Breaking the symmetry between left-handed and right-handed chiral optical modes in planar Fabry–Pérot (FP) microcavities would enable a variety of chiral light-matter phenomena, with applications in spintronics, polaritonics, and chiral lasing. Such symmetry breaking, however, has remained underexplored and has been purported to require Faraday mir...

A chiral bispyrene macrocycle designed for exclusive intermolecular excimer fluorescence upon aggregation was synthesized by a double hydrothiolation of a bis‐enol ether macrocycle followed by intramolecular oxidation of free thiols. Unusually high stereoselectivity was achieved for the thiol‐ene additions under templated conditions and Et3B/O2 rad...

A chiral bispyrene macrocycle designed for exclusive intermolecular excimer fluorescence upon aggregation was synthesized by a double hydrothiolation of a bis‐enol ether macrocycle followed by intramolecular oxidation of free thiols. Unusually high stereoselectivity was achieved for the thiol‐ene additions under templated conditions and Et 3 B/O 2...

We have studied the impact of achiral substituents on the chiral supramolecular architectures of diketopyrrolo[3,4‐c]pyrrole‐1,2,3‐1H‐triazole (DPP) dyes. We decorated the same chiral DPP motif with substituent groups on the nitrogen atoms of the lactam moiety: the hydrophobic n‐octyl alkyl chain, the hydrophilic tri(ethylene glycol) (TEG) chain an...

Phaeosphaeria sp., a lichen-associated fungus, produced six skeletally new dimeric spiciferones (1-6) and four known metabolites (7-10). The new structures were elucidated by spectroscopic analysis, and their absolute configurations were determined by electronic circular dichroism calculations. Compounds 1 and 3-6 represent the first examples of et...

We synthesized bis-aryl carbazole borane derivatives having emissive properties and axial chirality. The resolution of a thermally stable atropisomeric pair (compound 1b), due to a B-C chiral axis, was achieved by chiral stationary-phase high-performance liquid chromatography (CSP-HPLC). Complete photophysical properties of all compounds were measu...

A unique ring C-expanded angucyclinone, oxemycin A (1), and seven new ring-cleavage derivatives (2-5 and 9-11) were isolated from the marine actinomycete Streptomyces pratensis KCB-132, together with eight known analogues (6-8 and 12-16). Their structures were elucidated by spectroscopic analyses, single-crystal X-ray diffractions, and NMR and ECD...

Focus on aggregate structure: thin‐film mapping by Synchrotron Radiation Electronic Circular Dichroism Imaging (SR‐ECDi) reveals multiple aggregation modes of chiral oligothiophenes in the solid state. Two oligothiophenes with the same conjugated skeleton and different chiral pendants lead to mesoscopic domains allied with different supramolecular...

Polyproline I helical structures are often considered as the hidden face of their most famous geminal sibling, Polyproline II, as PPI is generally spotted only within a conformational equilibrium. We designed and synthesized a stable Polyproline I structure exploiting the striking tendency of (S)-indoline-2-carboxylic acid to drive the peptide bond...

Chiral quinacridines react up to four times, step‐by‐step, with α‐diazomalonates under RuII and RhII catalysis. By selecting the catalyst, [CpRu(CH3CN)3][PF6] (Cp=cyclopentadienyl) or Rh2(oct)4, chemo and regioselective insertions of derived metal carbenes are achieved in favor of mono‐ or bis‐functionalized malonate derivatives, respectively, (r.r...

Chiral quinacridines react up to four times, step‐by‐step, with a‐diazomalonates under Ru(II) and Rh(II) catalysis. By selecting the catalyst, [CpRu(CH 3 CN) 3 ][PF 6 ] (Cp = cyclopentadienyl) or Rh 2 (oct) 4 , chemo and regioselective insertions of derived metal carbenes are achieved in favor of mono‐ or bis‐functionalized malonate derivatives res...

A bioactive disubstituted nonenolide, named truncatenolide, was produced by Colletotrichum truncatum, which was collected from infected tissues of soybean showing anthracnose symptoms in Argentina. This is a devastating disease that drastically reduces the yield of soybean production in the world. The fungus also produced a new trisubstituted oct-2...

The study of chiroptical properties in thin films of chiral organic π‐conjugated dyes is more complex than isotropic solutions, due to the interference of macroscopic anisotropies often present in the solid state. The experimental circularly polarized (CP) absorption (electronic circular dichroism, ECD) and CP emission (circularly polarized lumines...

The chiroptical features of chiral diketopyrrolo[3,4‐c]pyrrole (DPP) derivatives have been only marginally investigated to date. In this regard, we have synthesized ad hoc four chiral DPP dyes, functionalized with enantiopure alkyl groups from natural sources either on the lactam moieties or on the terminal positions of the π‐conjugated backbone, t...

A family of bis[(R or S)‐N‐1‐(Ar)ethylsalicylaldiminato‐κ2N,O]‐Δ/Λ‐zinc(II) {Ar=C6H5 (ZnRL1 or ZnSL1), p‐CH3OC6H4 (ZnRL2 or ZnSL2) and p‐ClC6H4 (ZnRL3 or ZnSL3)} compounds was synthesized and investigated by multiple methods. They feature Λ/Δ‐chirality‐at‐metal induction along the pseudo‐C2 axis of the molecules. The chirality induction is quantita...

Novel chiral Er complexes based on both enantiomers of extended ⁱPrPyBox (2,6‐Bis[4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)]pyridine) show strong near‐infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to pot...

Novel chiral Er complexes based on both enantiomers of extended iPrPyBox (2,6‐Bis[4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)]pyridine) show strong near‐infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to pot...

The study of the chiroptical properties of thin‐film samples of two chiral benzo[1,2‐b:4,5‐b’]dithiophene‐based oligothiophenes with optoelectronic properties was carried out at Diamond B23 beamline using the synchrotron radiation electronic circular dichroism imaging (SR‐ECDi) facility. The experimental results support the hypothesis that the non‐...

Organic compounds showing circularly polarized luminescence (CPL) are at the forefront of novel applications and technologies. Here we show the synthesis and chiroptical properties of pyrene and perylene derivatives of inexpensive chiral scaffolds: isomannide and isosorbide. Low‐intensity ECD spectra were obtained, suggesting the absence of chromop...

Thanks to the concept of synchrotron radiation ECD imaging (SR-ECDi) applied to the active pharmaceutical ingredient Finasteride, we obtained an exclusive insight into the critical role played by the anisotropy of local domains in solid-state ECD spectra. Our findings open a new way to interpret solid-state chiroptical measurements and will broaden...

Solid‐state ECD (ss‐ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm² with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss‐ECD recor...

We carried out a study of absorption (CD) and emission (CPL) chiroptical properties in the NIR region of two sets of Yb, Tm and Er complexes. The two complexes include a D3 symmetric, [TMG-H+]3Ln(BINOLate)3 (Ln = Yb, Tm, Er; TMG = 1,1,3,3-tetramethylguanidine; BINOLate = 1,1'-bi-2-naphtholate), and a tetrakis, C4 symmetric, CsLn(hfbc)4 (Ln = Yb, Tm...

The application of the exciton chirality method (ECM) to interpret electronic circular dichroism (ECD) spectra is a well‐established and still popular approach to assign the absolute configuration (AC) of natural products, chiral organic compounds, and organometallic species. The method applies to compounds containing at least two chromophores with...

Angucyclines and angucyclinones represent the largest family of type II PKS-engineered natural products. Chemical analysis of a marine Streptomyces sp. KCB-132 yielded three new members, actetrophenone A (1) and actetrophenols A–B (2–3). Their structures were elucidated by NMR spectroscopy, X-ray crystallography and CD calculations. Actetrophenone...

Asymmetric synthesis of MOMs in gels: Gel phase synthesis of metal–organic materials (MOMs) resulted in homochiral MOMs, which were characterized by single crystal X‐ray diffraction. The chirality of the gelator dictated the handedness of the MOMs and the enantioselectivity was confirmed by solid‐state circular dichroism experiments. image

The enantiopure Schiff bases (R or S)-N-1-(X-C6H4)ethyl-2-hydroxy-1-naphthaldimine {X = H [(R or S)-HL1], p-CH3O [(R or S)-HL2], and p-Br [(R- or S)-HL3]} react with cobalt(II) acetate to give bis[(R or S)-N-1-(X-C6H4)ethyl-2-oxo-1-naphthaldiminato-κ²N,O]-Λ/Δ-cobalt(II) {X = H [Λ/Δ-Co-(R or S)-L1], p-CH3O [Λ/Δ-Co-(R or S)-L2], and p-Br [Λ/Δ-Co-(R o...

We report the asymmetric synthesis of homochiral metal–organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates. Asymmetric synthesis of MOMs in gels: Gel phase synthesis of metal–o...

Four racemic iminoflavan derivatives were synthesized by simple condensation at C‐4 position of flavanone. All new compounds were characterized by using ultraviolet‐visible, infrared and nuclear magnetic resonance spectroscopic techniques. A chiral chromatographic analysis of racemic mixtures was performed by direct chiral high‐performance liquid c...

A thorough experimental and computational study on the conformational properties of (S)-indoline-2-carboxylic acid derivatives has been conducted. Methyl (S)-1-acetylindoline-2-carboxylate, both a mimetic of proline and phenylalanine, shows a remarkable tendency toward the cis amide isomer when dissolved in polar solvents. This behavior is opposite...

A new cleistanthane nor-diterpenoid, named olicleistanone (1), was isolated as a racemate from the culture filtrates of Diplodia olivarum, an emerging pathogen involved in the aetiology of branch canker and dieback of several plant species typical of the Mediterranean maquis in Sardinia, Italy. When the fungus was grown in vitro on Czapek medium, o...

Two new penta- and tetrasubstituted cyclopentenones, named phaseocyclopentenones A and B (1 and 2), together with guignardone A (3), were isolated from Macrophomina phaseolina cultures. The phytopathogenic fungus was isolated from infected soybean tissues showing charcoal rot symptoms in Argentina. Charcoal rot is a devastating disease considering...

New bis-quinolinium chiral ionic liquids (CILs) were synthesized in good yields starting from isomannide and isosorbide by a straightforward procedure that maintains the absolute stereostructure of the isohexide scaffolds. Thermal gravimetric analysis and differential scanning calorimetry, aimed at investigating the short thermal stability and the...

Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecu...

A new cleistanthane nor -diterpenoid, named olicleistanone (1), was isolated as a racemate from the culture filtrates of Diplodia olivarum an emerging pathogen involved in the aetiology of branch canker and dieback of in several plant species typical of the Mediterranean maquis in Sardinia, Italy. When the fungus was grown in vitro on Czapek medium...

Controlling circularly polarized (CP) emission is key for both fundamental understanding and applications in the field of chiral photonics and electronics. Here, a completely new way to achieve this goal is presented. A luminescent thin film, made from a chiral conjugated phenylene bis‐thiophenylpropynone able to self‐assemble into ordered structur...

Ganorbifate A featuring an unprecedented 6/6/6/5/5 pentacyclic system, and ganorbifate B with an unusual 6/4/6/5/8/5 ring system were isolated from the fruiting body of Ganoderma orbiforme. Their structures were established...

A series of novel 1,4-dioxane analogs of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M1-M5 mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between CH2N+(CH3)3 chain in the 2-position and the cyclohexyl moiety in 6-position, showed pKi values for mAChRs higher...

Colletotrichum lupini: is the causal agent of lupin (Lupinus albus L.) anthracnose, a destructive seed-borne disease affecting stems and pods. Despite that several biological studies have been carried out on this pathogen, the production of secondary metabolites has not yet been investigated. Thus, a strain of C. lupini, obtained from symptomatic...

The synthesis of a chiral tetraarylmethane derivative is reported. The solvent effect on the CD spectra was observed for the solution. This is attributable to a molecular design with three of four aryl groups have the nitrogen atom at the ortho position with respect to the central carbon atom. This unique design was realized when a variety of trans...

Two new diterpenoids with tetrasubstituted 3-oxodihydrofuran substituents, named higginsianins D (1) and E (2), were isolated from the mycelium of the fungus Colletotrichum higginsianum grown in liquid culture. They were characterized as methyl 2-[6-hydroxy-5,8a-dimethyl-2-methylene-5-(4-methylpent-3-enyl)-decahydronaphthalen-1-ylmethyl]-4,5-dimeth...

Moving from the simple concept that reflection onto a mirror surface changes the handedness of circularly polarized light, we describe what happens to the emergent polarization in two different cases after reflection on a back mirror. In the first case, a regular emitter is taken into account, where reflection has the effect to destroy the emergent...

Phenyl‐pyrazinyl‐2‐pyridyl‐2‐pyrimidinylmethane (1) has been synthesized in four steps from 2‐(chloromethyl)pyridine. This compound is chiral and expected to show metal‐coordinating ability because three of four aryl groups have the nitrogen atom at ortho‐position with respect to the central carbon atom. The X‐ray crystallographic analysis of rac‐1...

(±)‐Pratenone A (1), the first representative of natural 3‐(1‐naphthyl)‐2‐benzofuran‐1(3H)‐one polyketides, was isolated from a marine‐derived Streptomyces pratensis strain KCB‐132 together with three other new analogues (2−4). Its structure was assigned by spectroscopic analysis, and the absolute configurations of the two enantiomers separated by...

A new phytotoxic tetrasubstituted chromen-4-one (1) and a new hexasubstituted benzophenone (2), named rabenchromenone and rabenzophenone, respectively, were isolated from the culture filtrates of Fimetariella rabenhorstii, an oak-decline-associated fungus in Iran. Rabenchromenone and rabenzophenone, isolated together with known moniliphenone (3) an...

Different phytotoxic metabolites were isolated from the organic extract of Neofusicoccum luteum, Neofusicoccum australe, and Neofusicoccum parvum, causal agents of Botryosphaeria dieback in Australia. N. luteum produced a new disubstituted furo-α-pyrone, a hexasubstituted anthraquinone, and a trisubstituted oxepi-2(7H)-one, luteopyroxin (4), neoant...

A series of oligomers containing alternate L-Ala and pGlu (pyroglutamic acid) both in the L and D form have been prepared and conformationally investigated by X-ray, NMR, UV/ECD, IR/VCD and molecular modelling. X-ray diffraction analysis was possible for the shortest oligomers LL-1 and LD-1. Molecular dynamics simulations of the oligomers demonstra...

A new tetranorditerpenoid (1), two new labdane diterpenoids (2, 3), and nine known analogues (4-12) were isolated from the rhizomes of Amomum villosum var. xanthioides. Compound 1 is an unprecedented rearranged tetranorlabdane diterpenoid, featuring a 6/6/5 fused tricarbocyclic skeleton with an α,β-unsaturated cyclopentenone unit, while 2 is a stru...

We demonstrated the hitherto unknown property of the mycotoxin sterigmatocystin (STC) to provide homogeneous solutions in aqueous medium by forming a unique aggregate type (not formed by analogous aflatoxins), characterized by exceptionally strong circular dichroism (CD) bands in the 300-400 nm range. Results showed that these CD bands do not origi...

The chiral spin–flip luminophore [Cr(ddpd) 2 ] ³⁺ can be resolved into enantiopure material by chiral HPLC. The pure enantiomers display strong CPL activity for the corresponding near-IR phosphorescence.

We highlight the power of electronic circular dichroism imaging (CDi), a technique developed at Diamond Light Source B23 beamline for synchrotron radiation circular dichroism (SRCD) to detect local domains of chiral supramolecular order in thin films of chiral oligomers and polymers. The highly brilliant and collimated beamlight of B23 enabled CDi...