Copper-based LECs with a maximum efficacy of 3.0 cd A−1 (luminance = 145 cd m−2) or with lifetimes >80 h have been achieved.

A complete series of experimental and theoretical investigations on the supramolecular polymerization of chiral (1 and 2) and achiral (3) oligo­(phenylene ethynylene) tricarboxamides (OPE-TAs) is reported. The performance of seargents-and-soldiers (SaS) and majority rules (MR) experiments has allowed deriving a full set of thermodynamic parameters, including the helix reversal penalty (HRP) and the mismatch penalty (MMP). The results described illustrate the influence exerted by the number of stereogenic centers per monomeric unit and the temperature on the chiral amplification phenomenon. While the HRP decreases upon decreasing the number of chiral side chains, the MMP follows an opposite trend. The experimental trend observed in MR experiments contrasts with that reported for benzenetricarboxamides (BTAs), for which the chiral amplification ability increases by lowering the number of stereogenic centers or increasing the temperature. Theoretical calculations predict that the rotational angle between adjacent monomeric units in the stack (ca. 18°) gradually decreases when decreasing the number of branched chiral side chains and leads to higher MMP values, in good accord with the experimental trend. The reduction of the rotational angle gives rise to less efficient H-bonding interactions between the peripheral amide functional groups and is suggested to provoke a decrease of the HRP as experimentally observed. In BTAs, increasing the number of stereogenic centers per monomeric unit results in a negligible change of the rotation angle between adjacent units (ca. 65°), and, consequently, the steric bulk increases with the number of chiral side chains, leading to higher MMP values. The data presented herein contribute to shed light on the parameters controlling the transfer and amplification of chirality processes in supramolecular polymers, highlighting the enormous influence exerted by the size of the self-assembling unit on the final helical outcome.

A series of bis-cyclometalated iridium­(III) complexes of general formula [Ir­(ppy)2(N∧N)]­[PF6] (ppy– = 2-phenylpyridinate; N∧N = 2-(1H-imidazol-2-yl)­pyridine (1), 2-(2-pyridyl)­benzimidazole (2), 1-methyl-2-pyridin-2-yl-1H-benzimidazole (3), 2-(4′-thiazolyl)­benzimidazole (4), 1-methyl-2-(4′-thiazolyl)­benzimidazole (5)) is reported, and their use as electroluminescent materials in light-emitting electrochemical cell (LEC) devices is investigated. [2]­[PF6] and [3]­[PF6] are orange emitters with intense unstructured emission around 590 nm in acetonitrile solution. [1]­[PF6], [4]­[PF6], and [5]­[PF6] are green weak emitters with structured emission bands peaking around 500 nm. The different photophysical properties are due to the effect that the chemical structure of the ancillary ligand has on the nature of the emitting triplet state. Whereas the benzimidazole unit stabilizes the LUMO and gives rise to a 3MLCT/3LLCT emitting triplet in [2]­[PF6] and [3]­[PF6], the presence of the thiazolyl ring produces the opposite effect in [4]­[PF6] and [5]­[PF6] and the emitting state has a predominant 3LC character. Complexes with 3MLCT/3LLCT emitting triplets give rise to LEC devices with luminance values 1 order higher than those of complexes with 3LC emitting states. Protecting the imidazole N–H bond with a methyl group, as in complexes [3]­[PF6] and [5]­[PF6], shows that the emissive properties become more stable. [3]­[PF6] leads to outstanding LECs with simultaneously high luminance (904 cd m–2), efficiency (9.15 cd A–1), and stability (lifetime over 2500 h).