How Lewis Acidity of the Cationic Framework Affects KNaNbOF5 Polymorphism

Recent advances of oxyfluorides for nonlinear optical applications

Oxyfluorides exhibit rich crystal structures that provide a new perspective for designing new NLO materials.

Predicting the Structure Stability of Layered Heteroanionic Materials Exhibiting Anion Order

We report a workflow for heteroanionic materials discovery using Pauling's second rule to filter for and predict new candidate materials for synthesis with reduced computational overhead. Using oxyfluoride and oxynitride n = 1 Ruddlesden-Popper compounds as a use-case, we show that a minimization scheme based on the global instability index (GII) efficiently filters up to 50% of highly unstable candidate compositions based on crystal-chemistry grounds. We then validate the minimization scheme using density functional theory (DFT) calculations and find that unexpectedly the GII of stable heteroanionic materials is higher than that of homoanionic oxides owing to significant charge redistribution in compounds containing more than one anionic species. Using this workflow, we predict Sr₂AlO₃F to be stable and describe our attempts to synthesize a phase-pure material.

Effects of Charged Ligand Substituents on the Properties of the Formally Copper(III)-Hydroxide ([CuOH]2+) Unit

With the goal of understanding how distal charge influences the properties and hydrogen atom transfer (HAT) reactivity of the [CuOH]2+ core proposed to be important in oxidation catalysis, the complexes [M]3[SO3LCuOH] (M = [K(18-crown-6)]+ or [K(crypt-222)]+) and [NMe3LCuOH]X (X = BArF4- or ClO4-) were prepared, in which SO3- or NMe3+ substituents occupy the para positions of the flanking aryl rings of the supporting bis(carboxamide)pyridine ligands. Structural and spectroscopic characterization showed that the [CuOH]+ cores in the corresponding complexes were similar, but cyclic voltammetry revealed the E1/2 value for the [CuOH]2+/[CuOH]+ couple to be nearly 0.3 V more oxidizing for the [NMe3LCuOH]2+ than the [SO3LCuOH]- species, with the latter influenced by interactions between the distal -SO3- substituents and K+ or Na+ counterions. Chemical oxidations of the complexes generated the corresponding [CuOH]2+ species as evinced by UV-vis spectroscopy. The rates of HAT reactions of these species with 9,10-dihydroanthracene to yield the corresponding [Cu(OH2)]2+ complexes and anthracene were measured, and the thermodynamics of the processes were evaluated via determination of the bond dissociation enthalpies (BDEs) of the product O-H bonds. The HAT rate for [SO3LCuOH]- was found to be ∼150 times faster than that for [NMe3LCuOH]2+, despite finding approximately the same BDEs for the product O-H bonds. Rationales for these observations and new insights into the roles of supporting ligand attributes on the properties of the [CuOH]2+ unit are presented.