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Chiral diketopyrrolopyrroles appended with enantiomeric ethyl lactate functions through an ether linkage to the aryl backbone of the chromophore were synthesized via the Mitsunobu reaction. The molecules have good solubility and excellent optical properties, high molar absorption coefficients, and fluorescence quantum yields. Helical aggregates with circular dichroism arising from the supramolecular arrangement are seen in both solution and thin films, and the aggregates also display circularly polarized luminescence (glum ≈ ±0.1). The molecules assemble to give monolayers on graphite and precipitate from solution forming supramolecular twisted tapes hundreds of microns long. [ABSTRACT FROM AUTHOR]

The synthesis, spectroelectrochemical and structural characteristics of highly electron-accepting diketopyrrrolopyrrole (DPP) molecules with adjoining pyridinium rings is reported, along with an assessment of their toxicity, which is apparently low. The compounds show reversible electrochemistry and in one subfamily a massive increase in molar extinction coefficient upon electrochemical reduction. [ABSTRACT FROM AUTHOR]

The solid state supramolecular interactions of diketopyrrolopyrrole derivatives (DPPs) and their correlation with thin film optical properties are of particular interest because of the applications of these materials in organic electronics. In this study, we report the single crystal X-ray structures of several phenyl DPP derivatives, containing 4-methoxyphenyl, 4-hydroxyphenyl and 4-((tetrahydro-2H-pyran-2-yl)oxy)phenyl aryl units, and show how subtle changes in the substituent chains at side or end positions of the chromophore can lead to very different packing. They are compared to their phenyl counterpart to explore how the nature of both the alkyl chain and the aryl unit influence the optical properties that have been measured in solid and solution states. Importantly, for the three families of N-substituted compounds studied, the structures are changed by the conformation of the molecules and are apparently dominated by crystal packing effects where edge-to-face interactions are favoured rather than π stacking, with only one of the compounds showing a flat form, promoted by intermolecular contacts between the aromatic regions. It is therefore possible that the twist between DPP and phenyl units in crystals of DPPs results from edge-to-face interactions (rather than steric interactions between the N-substituent and the protons attached to the aromatic ring) that might be overcome in more extended structures. Hydrogen bonding dominates the packing to generate chains of DPP units for phenol derivatives. Remote bulky groups do affect the core conformation. The emission of the materials as thin films is dominated by local effects in the packing of the materials that are unique for each case as the structures are distinct from one another. Charge mobility (as calculated from the crystal structures) is not favoured because of twisted conformations and large displacement, but the sometimes high emission and large Stokes shift could make the materials interesting for other purposes, such as light emitters. [ABSTRACT FROM AUTHOR]

A series of symmetrically bis‐4‐methoxybenzyl (4MB) N‐substituted 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP) derivatives have been synthesized. The 4MB unit makes the DPP core soluble, and shows subtle modification of up to 0.2 eV in ground and excited states of the core when compared with related alkyl derivatives. Absorption and emission spectroscopy, as well as electrochemical and computational methods have been employed to prove the importance of the peripheral aryl units on the donor/ acceptor properties of the molecules. The 4MB products are highly fluorescent (quantum yields approaching 100 % in solution), with a unique distribution of frontier states shown by spectroelectrochemistry. The solid‐state fluorescence correlates with the X‐ray crystal structures of the compounds, a Stokes shift of approximately 80 nm is seen for two of the compounds. The frontier energy levels show that this subtle substitutional change could be of future use in molecular energy level tailoring in these, and related, materials for organic (opto)electronics. [ABSTRACT FROM AUTHOR]

The alkylation of 1,4-diketo-3,6-arylpyrrolo[3,4-c]pyrroles (ArDPP) is one of the most important steps in the synthesis of soluble materials based on these molecules and the polymers derived from them (that are employed widely in putative organic solar cells). Here we report an improvement in their method of synthesis replacing habitual solvent and base. Compared with more usual conditions, we employed acetonitrile as solvent to give higher or similar yields, with less toxic and hazardous waste, lower reaction time and temperature, and allows recycling of unreacted starting materials. Unlike dimethylformamide and N-methylpyrrolidone, which are the most commonly employed solvents. Our reaction conditions have been tested on three different ArDPPs (Ar = thiophene, phenyl and 4-methoxyphenyl) with a variety of linear and branched alkyl reagents. The results show similar and improved results in comparison with the published reports while reducing the waste and hazard of the reaction, as well as simplifying the purification of the products in many cases. Overall this method has lower environmental impact, is more cost effective and requires neither the use of dry solvent nor inert atmosphere. [ABSTRACT FROM AUTHOR]

The article presents a brief overview of sustainable and responsible investing (SRI) in the U.S. According to survey conducted by the Social Investment Forum Foundation (SIF), about 2.5 trillion dollars in assets are held by institutional investors. It is stated that interest in SRI issues is not a passing phenomenon, but it has gathered adherents over the last 15 years.