Electrochemistry of cyclic triimidazoles and their halo derivatives: A casebook for multiple equivalent centers and electrocatalysis

A family of cyclic triazines, based on the triimidazo[1,2-a:1\u2032,2\u2032-c:1\u2033,2\u2033-e][1,3,5]triazine scaffold, has recently caught attention due to its variegated solid state photoluminescent properties (e.g., crystallization induced emission, fluomechanochromism, dual fluorescence, room temperature ultralong phosphorescence), tuned by proper functionalization of the cyclic core. From an electrochemical point of view, this family of heteroaromatic cyclic triazines is unexplored. A cyclic voltammetry study is here performed aiming to clarify structure/electroactivity relationship. The peculiar molecular structure of this class of molecules offers a multi-approach case study, spanning from multiple equivalent redox site interactions in small hoops (due to ideally C3h symmetry) to carbon-halogen bond reactivity in the presence of catalytic metal electrode surfaces (for \u2013Br and \u2013I derivatives). Results point to a poor heteroannular aromaticity along the rigid, planar cyclotrimer, with each equivalent redox site acting quite independently. An unusually higher electrocatalytic performance of gold with respect to silver electrode for the electrocleavage of carbon-halogen bonds (that decreases by increasing number of halo substituents) is tentatively explained in term of a specific interaction between gold and the nitrogen-rich planar cyclotrimer platform

Solid-state Nonlinear Optical Properties of Mononuclear Copper(II) Complexes with Chiral Tridentate and Tetradentate Schiff Base Ligands

Salen-type metal complexes have been actively studied for their nonlinear optical (NLO) properties, and push-pull compounds with charge asymmetry generated by electron releasing and withdrawing groups have shown promising results. As a continuation of our research in this field and aiming at solid-state features, herein we report on the synthesis of mononuclear copper(II) derivatives bearing either tridentate N2O Schiff bases L(a-c)- and pyridine as the forth ancillary ligand, [Cu(La-c)(py)](ClO4) (1a-c), or unsymmetrically-substituted push-pull tetradentate N2O2 Schiff base ligands, [Cu(5-A-5'-D-saldpen/chxn)] (2a-c), both derived from 5-substituted salicylaldehydes (sal) and the diamines (1R,2R)-1,2-diphenylethanediamine (dpen) and (1S,2S)-1,2-diaminocyclohexane (chxn). All compounds were characterized through elemental analysis, infrared and UV/visible spectroscopies, and mass spectrometry in order to guarantee their purity and assess their charge transfer properties. The structures of 1a-c were determined via single-crystal X-ray diffraction studies. The geometries of cations of 1a-c and of molecules 2a-c were optimized through DFT calculations. The solid-state NLO behavior was measured by the Kurtz-Perry powder technique @1.907 µm. All chiral derivatives possess non-zero quadratic electric susceptibility (χ(2)) and an efficiency of about 0.15-0.45 times that of standard urea

The deep circumflex iliac artery free flap in maxillofacial reconstruction: a comparative institutional analysis

Purpose: The aim of the present study was to perform a comparative analysis of the utility, outcomes, and complications of DCIA (deep circumflex iliac artery) flap for the reconstruction of maxillofacial defects between two institutions that continue to use the DCIA flap as a reconstructive resource. Materials and methods: This retrospective analysis included a total of 68 patients (mean age 51.1 years) at the University Hospital of Parma, Parma, Italy, and the University of Maryland, Baltimore, USA, between January 2010 and April 2019. Results: No statistical differences were found in relation to the site of reconstruction (p = 0.09), bone graft quantity (p = 0.93), rehabilitation with dental implants (p = 0.464), length of hospitalization (p = 0.086), BMI (0.677), swallow function (p = 0.419), medical comorbidities (p = 0.933), pre-existing radiation (p = 0.691), adjuvant treatment (p = 0.298), ECOG-PS pre-and post-surgery (p = 0.329; p = 0.545), and flap failure: one partial failure observed (p = 0.412) and donor site morbidities (p = 0.742). A noted trend to increased risk of hernia without the use of a primary mesh repair was observed (p = 0.059). Conclusion: The DCIA free flap represents a useful and reliable reconstructive flap for maxillofacial reconstruction. Reconstructive microvascular surgeons should be proficiently trained in this flap technique for its consideration as a first-line option in maxillofacial reconstruction

Prenatal diagnosis of X-linked adrenoleukodystrophy associated with isolated pericardial effusion

This is the first reported case of fetal pericardial effusion in association with X-linked adrenoleukodystrophy and hypocortisolism from a nonautoimmune cause. Our hypothesis is that in experienced hands and after accurate genetic counseling, isolated pericardial effusion can constitute an indication for a severe metabolic disease

Intrinsic and Extrinsic Heavy-Atom Effects on the Multifaceted Emissive Behavior of Cyclic Triimidazole

Considering that heavy halogen atoms can be used to tune the emissive properties of organic luminogens, the understanding of their role in photophysics is fundamental for materials engineering. Here, the extrinsic and intrinsic heavy-atom effects on the photophysics of organic crystals were separately evaluated by comparing cyclic triimidazole (TT) with its monoiodo derivative (TTI) and its co-crystal with diiodotetrafluorobenzene (TTCo). Crystals of TT showed room-temperature ultralong phosphorescence (RTUP) originated from H-aggregation. TTI and TTCo displayed two additional long-lived components, the origin of which is elucidated through single-crystal X-ray and DFT/TDDFT studies. The results highlight the different effects of the I atom on the three phosphorescent emissions. Intrinsic heavy-atom effects play a major role on molecular phosphorescence, which is displayed at room temperature only for TTI. The H-aggregate RTUP and the I c5 c5 c5N XB-induced (XB=halogen bond) phosphorescence on the other side depend only on packing features

Long-living optical gain induced by solvent viscosity in a push-pull molecule

The combination of continuum and ultrafast pump-probe spectroscopy with DFT and TDDFT calculations, in viscous and non-viscous environments, is effective in unraveling important features of the twisted intramolecular charge transfer mechanism in a new push-pull molecule that possesses aggregation induced emission properties. Long-living optical gain is found when this mechanism is inhibited, highlighting the importance of the environment rigidity in the design of materials for photonic applications

Protonated N,N -Dioxide-4,4 -bipyridine, an Interesting Synthon for the Building of Polar H-Bonded Networks?

A slow liquid-gas diffusion method in strong acid conditions has allowed stabilizing for the first time in the solid state the diprotonated form of the 4,4-bipyridine-N,N-dioxide (bp4do), H(2)bp4do(2+) as two polymophs of the chloride salt (H(2)bp4do)Cl-2, while in the presence of a metallic salt M((III))Br-3 (M = Bi, Sb), the monoprotonated form Hbp4do(+) is mainly stabilized as (Hbp4do)(2)[Sb2Br8] and (H(2)bp4do)(Hbp4do)(4-)[Bi4Br18]center dot 2H(2)O. The dehydration of this last phase leads to (H(2)bp4do)(Hbp4do)(4)[Bi4Br18]. In the structures of (H(2)bp4do)Cl-2 salts, the hydroxyl H atoms point toward the chloride anions leading to close (O)H center dot center dot center dot Cl contacts in the range 1.831-1.839 angstrom. A one-dimensional network of H-bonded Hbp4do(+) cations is found in the structure of (Hbp4do)(2)[Sb2Br8], whereas H-bonded supramolecular cations of five entities are found in the structures of bromobismuthate salts. In all the halometallate structures, X-ray analyses (293 K and 120 K data) did not allow us to locate the acid H atoms of protonated bp4do molecules certainly due to a disorder phenomenon but also revealing an asymmetrical H-bonding situation. The bromobismuthate hybrids are nonlinear optical active with a powder second harmonic generation efficiency being half that of urea

Fluorine-induced J-aggregation enhances emissive properties of a new NLO push–pull chromophore

A new fluorinated push–pull chromophore with good second-order NLO properties even in concentrated solution shows solid state intermolecular aryl–fluoroaryl interactions leading to J-aggregates with intense solid state luminescence

Tuning the Linear and Nonlinear Optical Properties of Pyrene-Pyridine Chromophores by Protonation and Complexation to d10 Metal Centers †

The linear and second-order nonlinear optical (NLO) properties of two pyrene-pyridine chromophores, namely, 4-(pyren-1-yl)pyridine (L1) and 4-(2-(pyren-1-yl)ethyl)pyridine (L2), were investigated and modulated by performing protonation/deprotonation cycles or by complexation to d10 metal centers such as Zn(II) and Cu(I) to form the monomeric [Zn(CH3CO2)2(L1)2] complex and the [CuI(L2)]n coordination polymer, respectively. The structures of L1, L2, [Zn(CH3CO2)2(L1)2] and [CuI(L2)]n were determined by means of single-crystal X-ray diffraction studies. The NLO response, measured by the electric-field-induced second harmonic generation (EFISH) technique, was positive for both chromophores and showed an inversion of the sign after exposure to HCl vapors. This process was completely reversible and the original values were restored by simple exposure to NH3 vapors. Coordination of L1 to Zn(II) also resulted in a negative NLO response, although smaller in magnitude compared to the protonated form, due to the weak Lewis acidity of the \u201cZn(CH3CO2)2\u201d fragment. The results were also interpreted on the basis of DFT/TDDFT calculation

An acido-triggered reversible luminescent and nonlinear optical switch based on a substituted styrylpyridine : EFISH measurements as an unusual method to reveal a protonation-deprotonation NLO contrast

Diphenyl-(4-{2-[4-(2-pyridin-4-yl-vinyl)-phenyl]-vinyl}-phenyl)-amine (DPVPA) constitutes a novel acido-triggered reversible luminescent and nonlinear optical switch. Remarkably, for the first time the Electric-Field Induced Second Harmonic generation (EFISH) technique is used to reveal a protonation-deprotonation NLO contrast