Successful adoption of defect management and carrier confinement strategies in Ruddlesden–Popper (RP) perovskites has driven the impressive improvements to performance of perovskite-based light-emitting diodes (PeLEDs) seen to date. Although functional additives have been advantageous in mitigating defects, their influence over crystallization behavior of RP (L2A m–1Pb m X3m+1) perovskites has yet to be fully studied. This is especially important for blue-emitting monohalide RP perovskites, where stringent control over m domain distribution is needed for efficient PeLEDs. Herein, we investigate the effect of triphenylphosphine oxide (TPPO) on crystallization behavior of blue RP (PBA2Cs m–1Pb m Br3m+1) perovskites. Despite TPPO addition, its absence in the resulting film eliminates its role as a passivating agent. Instead, TPPO acts as crystallization and phase distribution modulatorpromoting the formation of a narrow distribution of higher m domains with higher Br content. In doing so, an enhancement of ∼35% was noted with the champion device yielding efficiency of 3.8% at λ of 483 nm.

Instability of end-on superoxocopper(II) complexes, with respect to conversion to the corresponding peroxobridged complexes, has largely constrained their study to very low temperatures (< -80 C). This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of ligand systems bearing bulky aryl substituents that are primarily directed away from the metal centre, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support [Cu I (Ar3-TMPA)(NCMe)] + copper(I) complexes. Solutions of all three react with O2 to yield [Cu II ( 1 -O2 )(Ar3-TMPA)] + complexes that are stable against dimerization at all temperatures. Full binding of O2 is observed at sub-ambient temperatures and can be reversed by warming. The onset of oxygenation is ligand dependent, but can be observed at 25 C in the case of Ar = tpb and dpb. Furthermore, all three [Cu II ( 1 -O2 )(Ar3-TMPA)] + complexes are stable against self-decay at temperatures -20 C. This provides a wide temperature window over which these complexes can be studied, which was exploited by performing extensive reaction kinetics measurements for [Cu II ( 1 -O2 )(tpb3-TMPA)] + with a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2 values) versus oxidation potentials (Eox) for a range of phenols (i.e., a Marcus plot), construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicates that reaction with all substrates proceeds via H-atom transfer (HAT) to [Cu II ( 1 -O2 )(tpb3-TMPA)] + . In addition, evidence suggests that HAT reaction with the phenols studied proceeds with significant charge transfer, and that it involves full tunelling of both H and D atoms in the case of 1,2-diphenylhydrazine (DPH) and 4methoxy-2,6-di-tert-butylphenol (MeO-ArOH). Consistent with expectations for HAT, large entropic barriers ( S ) were measured for the substrates MeO-ArOH, DPH, triphenylhydrazine (TPH), and 1-benzyl-1,4-dihydronicotinamide (BNAH). Despite having the lowest X-H bond dissociation energy (BDE) amongst these substrates, the C-H substrate BNAH exhibits both the largest S and the second largest enthalpic barrier ( H ) to reaction. This is congruent with the expectation that oxidation of C-H bonds is kinetically challenging and the experimental observation that [Cu II ( 1 -O2 )(tpb3-TMPA)] + is only able to oxidize very weak C-H bonds, whereas it can oxidize moderately strong N-H bonds. ASSOCIATED CONTENTInformation. Experimental and synthetic procedures, X-ray crystallographic data collection and structural parameters, additional UV-Vis and resonance Raman spectra, and reaction kinetics data (PDF). Crystal structures of copper(II) complexes (CIF).This material is available free of charge via the Internet at http://pubs.acs.org.

The conjugate acids of 1,2,3-triazolylidene mesoionic carbenes can be prepared in a straightforward fashion by alkylation of 1substituted 1,2,3-triazoles. However, this becomes a much more challenging proposition when other nucleophilic centers are present, which has curtailed the development of ligands containing multiple 1,2,3-triazolylidene donors. Herein, methylation of a series of tris[(1aryl-1,2,3-triazol-4-yl)methyl]amines possessing both electron-rich and electron-deficient aromatic substituents, using Me 3 OBF 4 , is shown to proceed with much higher chemoselectivity under mechanochemical conditions than when conducted in solution. This provides a means to reliably access a series of tricationic tris[4-(1,2,3triazolium)methyl]amines in good yields. DFT calculations suggest that a potential reason for this change in regioselectivity is the difference between the background dielectric of the DCM solution versus the solid state, which is predicted to have a large effect on the relative thermodynamic driving force for alkylation of the tertiary amine center versus the triazole rings. Homoleptic silver complexes of the triazolylidene ligands derived therefrom, of formulas [Ag 3 (1a−d) 2 ](X) 3 (X − = BF 4 − , TfO − ), have been isolated and fully characterized. In the case of the ligand bearing the smallest aryl substituents, 1b, argentophilic interactions yield a triangular Ag 3 core. The [Ag 3 (1a−d) 2 ](X) 3 silver salts are viable agents for transmetalation to other transition metals, demonstrated here for cobalt. In the case of 1a, the complex [Co II (1a)(NCMe)](OTf) 2 was obtained. Therein, the bulky mesityl substituents enforce a tetrahedral geometry, in which only the triazolylidene donors of 1a coordinate (i.e., it acts as a tridentate ligand). Transmetalation of the less sterically encumbered ligand 1b yields six-coordinate cobalt(III) complexes, [Co III (1b)(Cl)(NCMe)](OTf) 2 and [Co III (1b)(NCMe) 2 ](OTf) 3 , in which the ligand coordinates in a tetradentate fashion. These are the first examples of tris(1,2,3triazolylidene) ligands containing an additional coordinating heteroatom and, more generally, of tetradentate 1,2,3-triazolylidene ligands. Crucially, we believe that the divergent chemoselectivity under mechanochemical conditions (vs conventional solutionbased chemistry) demonstrated herein offers a pathway by which other challenging synthetic targets, including further multidentate carbene ligands, can be prepared in superior yields.

Mixed-dimensional perovskites containing mixtures of organic cations hold great promise to deliver highly stable and efficient solar cells. However, although a plethora of relatively bulky organic cations have been reported...

Instability of end-on superoxocopper(II) complexes, with respect to conversion to the corresponding peroxobridged complexes, has largely constrained their study to very low temperatures (< -80 C). This limits their kinetic capacity to oxidize substrates. In response, we have developed a series of ligand systems bearing bulky aryl substituents that are primarily directed away from the metal centre, Ar3-TMPA (Ar = tpb, dpb, dtbpb), and used them to support [Cu I (Ar3-TMPA)(NCMe)] + copper(I) complexes. Solutions of all three react with O2 to yield [Cu II ( 1 -O2 )(Ar3-TMPA)] + complexes that are stable against dimerization at all temperatures. Full binding of O2 is observed at sub-ambient temperatures and can be reversed by warming. The onset of oxygenation is ligand dependent, but can be observed at 25 C in the case of Ar = tpb and dpb. Furthermore, all three [Cu II ( 1 -O2 )(Ar3-TMPA)] + complexes are stable against self-decay at temperatures -20 C. This provides a wide temperature window over which these complexes can be studied, which was exploited by performing extensive reaction kinetics measurements for [Cu II ( 1 -O2 )(tpb3-TMPA)] + with a broad range of O-H, N-H, and C-H bond substrates. This includes correlation of second order rate constants (k2 values) versus oxidation potentials (Eox) for a range of phenols (i.e., a Marcus plot), construction of Eyring plots, and temperature-dependent kinetic isotope effect (KIE) measurements. The data obtained indicates that reaction with all substrates proceeds via H-atom transfer (HAT) to [Cu II ( 1 -O2 )(tpb3-TMPA)] + . In addition, evidence suggests that HAT reaction with the phenols studied proceeds with significant charge transfer, and that it involves full tunelling of both H and D atoms in the case of 1,2-diphenylhydrazine (DPH) and 4methoxy-2,6-di-tert-butylphenol (MeO-ArOH). Consistent with expectations for HAT, large entropic barriers ( S ) were measured for the substrates MeO-ArOH, DPH, triphenylhydrazine (TPH), and 1-benzyl-1,4-dihydronicotinamide (BNAH). Despite having the lowest X-H bond dissociation energy (BDE) amongst these substrates, the C-H substrate BNAH exhibits both the largest S and the second largest enthalpic barrier ( H ) to reaction. This is congruent with the expectation that oxidation of C-H bonds is kinetically challenging and the experimental observation that [Cu II ( 1 -O2 )(tpb3-TMPA)] + is only able to oxidize very weak C-H bonds, whereas it can oxidize moderately strong N-H bonds.This material is available free of charge via the Internet at http://pubs.acs.org.