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Inverted perovskite solar cells (PSCs) have attracted increasing attention in recent years owing to their low-temperature fabrication proces s. However, they suffer from a limited number of electron transport materials available with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) to be the most widely studied based on its appropriate energy levels and high electron mobility. The low relative permittivity and aggregation tendency upon illumination of PCBM, however, compromises the solar cell efficiency whereas its modest hydrophobicity negatively impacts on the device stability. Alternative electron transport materials with desired properties and appropriate degree of hydrophobicity are thus desirable for further developments in inverted PSCs. Herein, we synthesize a triethyleneglycol C60 mono-adduct derivative (termed as EPF03) and test it as a novel electron transport material to replace PCBM in inverted PSCs based on a quadruple cation (RbCsMAFA) perovskite. We also compare this derivative with two novel fullerenes decorated with two (EPF01) or one dodecyl (EPF02) long side chains. The latter two fail to perform efficiently in inverted PSCs whereas the former enabled a power conversion efficiency of 18.43%, which represents a 9% improvement compared to the reference device using PCBM (17.21%). The enhanced performance mainly stems from improved electron extraction and reduced recombination enabled by the insertion of the large relative permittivity amongst other properties of EPF03. Furthermore, our results indicate that triethylene glycol side chains can also passivate perovskite trap states, suppress ion migration and enhance photostability and long-term stability of EPF03 based perovskite solar cells. published

A straightforward, user-friendly, efficient protocol for the one pot, ZnI2-catalyzed allenylation of terminal alkynes with pyrrolidine and ketones, toward trisubstituted allenes, is described. Trisubstituted allenes can be obtained under either conventional heating or microwave irradiation conditions, which significantly reduces the reaction time. A sustainable, widely available, and low-cost metal salt catalyst is employed, and the reactions are carried out under solvent-free conditions. Among others, synthetically valuable allenes bearing functionalities such as amide, hydroxyl, or phthalimide can be efficiently prepared. Mechanistic experiments, including kinetic isotope effect measurements and density functional theory (DFT) calculations, suggest a rate-determining [1,5]hydride transfer during the transformation of the intermediate propargylamine to the final allene. The research project was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the "1st Call for H.F.R.I. Research Projects to support Faculty Members & Researchers and the procurement of high-cost research equipment grant" (Project Number: 16.Acronym: SUSTAIN). We thank Professor Thomas Mavromoustakos for his advice and support concerning the calculation of the relaxation delay times for the NMR analysis related to the kinetic isotope effect measurements. We also acknowledge the contribution of COST Action CA15106 (C-H Activation in Organic Synthesis.CHAOS). We also thank the Spanish Ministerio de Ciencia e Innovacion (PID2019-110008GB-I00) and IZO-SGI SGIker of UPV/EHU for financial and human support. The Special Account for Research Grants of the National and Kapodistrian University of Athens is also gratefully acknowledged for funding (research program 70/4/17454).

“Green chemistry” and sustainable catalysis are increasingly attracting significant attention, in both industry and academia. Multicomponent reactions aim towards “greener” chemical transformations, mostly due to their step economy. The A3 coupling is a widely-studied multicomponent reaction, bringing together aldehydes, amines, and alkynes in a one pot manner, towards tertiary propargylamines, which are highly useful compounds with a variety of applications. The majority of reported synthetic protocols towards propargylamines require the preceding preparation of other starting materials, resulting in the need for increased time investment and cost, as well as encompassing a negative environmental impact. On the other hand, the A3 reaction requires simple, widely-available starting materials and can be completed in one step, making it immensely superior to the conventional approaches. This transformation is carried out by transition metal-based catalysts, which generate the necessary metal acetylides and merge them with the in situ generated aldimines/aldimine cations. Unfortunately, though, due to stereochemical and electronic reasons, ketimines/ketimine cations are way less reactive than their aldimine/aldimine cation counterparts, against nucleophilic attack, making their use in analogous transformations more challenging. This is why only 10 years have passed since the first KA2 reaction was reported (i.e. the one-pot coupling of a ketone with an amine and an alkyne towards quaternary propargylamines). The present review article provides a brief introduction to multicomponent reactions, the existing conventional synthetic routes towards propargylamines, and the A3 coupling reaction. A detailed, critical discussion of all KA2 homogeneous and heterogeneous catalytic protocols, the mechanisms proposed, as well as the difficulties encountered and the strategies employed to circumvent them follows. © 2020 Elsevier B.V.

Two new Zn(II) complexes with tridentate hydrazone-based ligands (condensation products of 2-acetylthiazole) were synthesized and characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy and single crystal X-ray diffraction methods. The complexes 1, 2 and recently synthesized [ZnL3(NCS)2] (L3 = (E)-N,N,N-trimethyl-2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethan-1-aminium) complex 3 were tested as potential catalysts for the ketone-amine-alkyne (KA2) coupling reaction. The gas-phase geometry optimization of newly synthesized and characterized Zn(II) complexes has been computed at the density functional theory (DFT)/B3LYP/6–31G level of theory, while the highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO and LUMO) energies were calculated within the time-dependent density functional theory (TD-DFT) at B3LYP/6-31G and B3LYP/6-311G(d,p) levels of theory. From the energies of frontier molecular orbitals (HOMO–LUMO), the reactivity descriptors, such as chemical potential (µ), hardness (η), softness (S), electronegativity (χ) and electrophilicity index (ω) have been calculated. The energetic behavior of the investigated compounds (1 and 2) has been examined in gas phase and solvent media using the polarizable continuum model. For comparison reasons, the same calculations have been performed for recently synthesized [ZnL3(NCS)2] complex 3. DFT results show that compound 1 has the smaller frontier orbital gap so, it is more polarizable and is associated with a higher chemical reactivity, low kinetic stability and is termed as soft molecule. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

“Green chemistry” and sustainable catalysis are increasingly attracting significant attention, in both industry and academia. Multicomponent reactions aim towards “greener” chemical transformations, mostly due to their step economy. The A3 coupling is a widely-studied multicomponent reaction, bringing together aldehydes, amines, and alkynes in a one pot manner, towards tertiary propargylamines, which are highly useful compounds with a variety of applications. The majority of reported synthetic protocols towards propargylamines require the preceding preparation of other starting materials, resulting in the need for increased time investment and cost, as well as encompassing a negative environmental impact. On the other hand, the A3 reaction requires simple, widely-available starting materials and can be completed in one step, making it immensely superior to the conventional approaches. This transformation is carried out by transition metal-based catalysts, which generate the necessary metal acetylides and merge them with the in situ generated aldimines/aldimine cations. Unfortunately, though, due to stereochemical and electronic reasons, ketimines/ketimine cations are way less reactive than their aldimine/aldimine cation counterparts, against nucleophilic attack, making their use in analogous transformations more challenging. This is why only 10 years have passed since the first KA2 reaction was reported (i.e. the one-pot coupling of a ketone with an amine and an alkyne towards quaternary propargylamines). The present review article provides a brief introduction to multicomponent reactions, the existing conventional synthetic routes towards propargylamines, and the A3 coupling reaction. A detailed, critical discussion of all KA2 homogeneous and heterogeneous catalytic protocols, the mechanisms proposed, as well as the difficulties encountered and the strategies employed to circumvent them follows.