Active Learning of Ligands That Enhance Perovskite Nanocrystal Luminescence.

Ligands play a critical role in the optical properties and chemical stability of colloidal nanocrystals (NCs), but identifying ligands that can enhance NC properties is daunting, given the high dimensionality of chemical space. Here, we use machine learning (ML) and robotic screening to accelerate the discovery of ligands that enhance the photoluminescence quantum yield (PLQY) of CsPbBr perovskite NCs. We developed a ML model designed to predict the relative PL enhancement of perovskite NCs when coordinated with a ligand selected from a pool of 29,904 candidate molecules.

In Pursuit of the Exceptional: Research Directions for Machine Learning in Chemical and Materials Science.

Exceptional molecules and materials with one or more extraordinary properties are both technologically valuable and fundamentally interesting, because they often involve new physical phenomena or new compositions that defy expectations. Historically, exceptionality has been achieved through serendipity, but recently, machine learning (ML) and automated experimentation have been widely proposed to accelerate target identification and synthesis planning. In this Perspective, we argue that the data-driven methods commonly used today are well-suited for optimization but not for the realization of new exceptional materials or molecules.

Predicting inorganic dimensionality in templated metal oxides.

Amine-templated metal oxides are a class of hybrid organic-inorganic compounds with great structural diversity; by varying the compositions, 0D, 1D, 2D, and 3D inorganic dimensionalities can be achieved. In this work, we created a dataset of 3725 amine-templated metal oxides (including some metalloid oxides), their composition, amine identity, and dimensionality, extracted from the Cambridge Structure Database (CSD), which spans 71 elements, 25 main group building units, and 349 amines. We characterize the diversity of this dataset over reactants and in time.

Improving Data and Prediction Quality of High-Throughput Perovskite Synthesis with Model Fusion.

Combinatorial fusion analysis (CFA) is an approach for combining multiple scoring systems using the rank-score characteristic function and cognitive diversity measure. One example is to combine diverse machine learning models to achieve better prediction quality. In this work, we apply CFA to the synthesis of metal halide perovskites containing organic ammonium cations via inverse temperature crystallization.

Machine-Learning-Assisted Synthesis of Polar Racemates.

Racemates have recently received attention as nonlinear optical and piezoelectric materials. Here, a machine-learning-assisted composition space approach was applied to synthesize the missing M = Ti, Zr members of the Δ,Λ-[Cu(bpy)(HO)][MF]·3HO (M = Ti, Zr, Hf; bpy = 2,2'-bipyridine) family (space group: 2). In each (CuO, MO)/bpy/HF() (M = Ti, Zr, Hf) system, the polar noncentrosymmetric racemate (M-NCS) forms in competition with a centrosymmetric one-dimensional chain compound (M-CS) based on alternating Cu(bpy)(HO) and MF basic building units (space groups: Ti-CS (), Zr-CS (1̅), Hf-CS (2/)).

Anthropogenic biases in chemical reaction data hinder exploratory inorganic synthesis.

Most chemical experiments are planned by human scientists and therefore are subject to a variety of human cognitive biases, heuristics and social influences. These anthropogenic chemical reaction data are widely used to train machine-learning models that are used to predict organic and inorganic syntheses. However, it is known that societal biases are encoded in datasets and are perpetuated in machine-learning models.

Machine-learning-assisted materials discovery using failed experiments.

Inorganic-organic hybrid materials such as organically templated metal oxides, metal-organic frameworks (MOFs) and organohalide perovskites have been studied for decades, and hydrothermal and (non-aqueous) solvothermal syntheses have produced thousands of new materials that collectively contain nearly all the metals in the periodic table. Nevertheless, the formation of these compounds is not fully understood, and development of new compounds relies primarily on exploratory syntheses. Simulation- and data-driven approaches (promoted by efforts such as the Materials Genome Initiative) provide an alternative to experimental trial-and-error.

Role of noncovalent interactions in vanadium tellurite chain connectivities.

Structural differences in [V2Te2O10]n(2n-) chain metrics are directly ascribed to variations in noncovalent interactions in a series of organically templated vanadium tellurites, including [C6H17N3][V2Te2O10]·H2O, [C5H16N2][V2Te2O10], and [C4H14N2][V2Te2O10]. The noncovalent interaction (NCI) method was used to locate, quantify, and visualize intermolecular interactions in [C4H14N2][V2Te2O10] and [C5H16N2][V2Te2O10]. Variations in the van der Waals attractions between [1,4-diaminobutaneH2](2+) and [1,5-diaminopentaneH2](2+) result in divergent packing motifs for these cations, which causes a reorganization of N-H···O hydrogen bonding and variances in the [V2Te2O10]n(2n-) chain metrics.

Formation principles for vanadium selenites: the role of pH on product composition.

A series of organically templated vanadium selenites has been prepared under mild hydrothermal conditions. Single crystals of [C5H14N2][(VO)3(SeO3)2(HSeO3)4], [C5H14N2][VO(SeO3)2], [(R)-C5H14N2][(VO)3(SeO3)2(HSeO3)4], and [(S)-C5H14N2][(VO)3(SeO3)2(HSeO3)4] were grown from VOSO4, SeO2, and 2-methylpiperazine. Controlling the initial pH of the reaction mixture allows for one to select between the compounds found in the VOSO4/SeO2/2-methylpiperazine system, as the solution pH directly affects the relative ratio of the HSeO3(-) and SeO3(2-) concentrations.

catena-Poly[2,2',2''-nitrilo-tris-(ethan-aminium) [tri-μ-oxido-tris-[dioxido-vanadate(V)]] monohydrate].

The title compound, {(C6H21N4)[V3O9]·H2O} n , crystallizes as a salt with [trenH3](3+) cations [tren is tris-(2-amino-eth-yl)amine], and one-dimensional anionic {[V(V)O3](-)} n (metavanadate) chains along the c-axis direction. Three crystallographically distinct V(V) sites and one occluded water mol-ecule are present for every [trenH3](3+) cation in the unit cell. The {[V(V)O3](-)} n chains are composed of vertex-sharing [VO4] tetra-hedra and have a repeat unit of six tetra-hedra.

Role of hydrogen-bonding in the formation of polar achiral and nonpolar chiral vanadium selenite frameworks.

A series of organically templated vanadium selenites have been prepared under mild hydrothermal conditions. Single crystals were grown from mixtures of VOSO(4), SeO(2), and either 1,4-dimethylpiperazine, 2,5-dimethylpiperazine, or 2-methylpiperazine in H(2)O. Each compound contains one-dimensional [VO(SeO(3))(HSeO(3))](n)(n-) secondary building units, which connect to form three-dimensional frameworks in the presence of 2,5-dimethylpiperazine or 2-methylpiperazine.

The role of stereoactive lone pairs in templated vanadium tellurite charge density matching.

The role of charge density matching was investigated in the formation of templated vanadium tellurites under mild hydrothermal conditions. Reactions were conducted using a fixed NaVTeO(5):amine ratio in an ethanol/water solution to isolate the effects of amine structure. The use of 1,4-diaminobutane, 1,3-diaminopropane, and piperazine resulted in three distinct vanadium tellurite connectivities, [V(2)Te(2)O(10)](n)(2n-) chains, [V(2)TeO(8)](n)(2n-) layers, and [V(2)Te(2)O(10)](n)(2n-) layers, respectively.

Noncentrosymmetry in new templated gallium fluorophosphates.

Two new noncentrosymmetric polar gallium fluorophosphates have been synthesized under mild hydrothermal conditions through the use of enantiomorphically pure sources of either R-2-methylpiperazine or S-2-methylpiperazine. A centrosymmetric analogue was also prepared using a racemic source of the amine. Novel [Ga(3)F(PO(4))(4)](n)(4n-) layers, constructed from [Ga(3)O(3)F(PO(4))(4)] building units, are observed in all three compounds.

Synthetic approaches for noncentrosymmetric molybdates.

The use of second-order Jahn-Teller active Mo (VI) centers and chiral organic amines is discussed as an approach to crystallographic noncentrosymmetry. Several series of reactions, conducted under mild hydrothermal conditions, were designed to probe important reaction variables. Correlations between reagent and solvent concentrations and the molybdate structure were investigated using composition space analysis, which allows for the isolation of specific reaction variables.

[Mo16O53F2]12-: a new polyoxofluoromolybdate anion.

Single crystals of a new beta-octamolybdate salt containing protonated 1,4-diazabicyclo[2.2.2]octane cations were prepared under mild hydrothermal conditions.

Directed synthesis of noncentrosymmetric molybdates using composition space analysis.

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown.

The role of amine sulfates in hydrothermal uranium chemistry.

A series of novel uranium sulfates containing organic structure directing cations has been synthesized from amine sulfate precursors under hydrothermal conditions. The amine sulfates act as a soluble source of the protonated amines and sulfate ions at low temperature and provide a reaction pathway in which no amine decomposition is observed. The protonated amines act as both space fillers and hydrogen-bond donors in the three-dimensional structure.

The effects of hydrofluoric acid addition on the hydrothermal synthesis of templated uranium sulfates.

The effect of employing hydrofluoric acid as a mineraliser in the formation of organically templated uranium sulfate materials has been studied. Variable amounts of HF((aq)) were added to a series of reaction gels in which all other reactant concentrations were invariant, resulting in the formation of three different phases, depending upon the fluoride concentration. Two of these phases are novel; [N(2)C(4)H(14)][UO(2)(H(2)O)(SO(4))(2)] is a new templated uranium sulfate, containing anionic [UO(2)(H(2)O)(SO(4))(2)](2-) chains that hydrogen bond to one-another forming pseudo-layers, and [N(2)C(4)H(14)][UO(2)F(SO(4))](2) is the first example of a templated uranium sulfate fluoride, which consists of uranium fluoride chains linked by sulfate groups to form [UO(2)F(SO(4))](-) layers.

[C5H14N2][(MoO3)3(SO4)].H2O: sulfated alpha-molybdena chains.

Recent work in the preparation of organically templated metal sulfates under hydrothermal conditions has been extended to include the sulfation of alpha-molybdena through the synthesis of [C(5)H(14)N(2)][(MoO(3))(3)(SO(4))].H(2)O. Single crystals were grown under hydrothermal conditions from molybdenum oxide, water, sulfuric acid, and an enantiomerically pure (R)-2-methylpiperazine source and characterized using both single-crystal X-ray diffraction and infrared spectroscopy.

Kinetic and mechanistic investigations of hydrothermal transformations in zinc phosphates.

The room-temperature crystallization of [C(6)N(2)H(18)][Zn(HPO(4))(H(2)PO(4))(2)], an organically templated zinc phosphate containing [Zn(2)(HPO(4))(2)(H(2)PO(4))(4)](4)(-) molecular anions, and its transformation to compounds containing either one- or two-dimensional inorganic components, [C(6)N(2)H(18)][Zn(3)(H(2)O)(4)(HPO(4))(4)], [C(4)N(2)H(12)][Zn(HPO(4))(2)(H(2)O)], or [C(3)N(2)H(6)][Zn(4)(OH)(PO(4))(3)], under hydrothermal conditions were studied in-situ using energy-dispersive X-ray diffraction. The ability to collect data during reactions in a large volume ( approximately 23 mL) Teflon-lined autoclave under real laboratory conditions has allowed for the elucidation of kinetic and mechanistic information. Kinetic data have been determined by monitoring changes in the integrated peak intensities of Bragg reflections and have been modeled using the Avrami-Erofe'ev expression.

A novel coordination mode for pentalene in trinuclear chromium complexes.

The first chromium pentalene complexes have been characterized; in these the ligand displays a hitherto-unknown bonding mode whereby a dimeric [Cr(Cp*)](2)(mu-OR) unit is bound (mu:eta(2):eta(2))- to one face, and Cp*Cr is bound eta(5)- to the other. The magnetic properties of these compounds can be understood as the superposition of those of a chromocene and an antiferromagnetically coupled Cr[bond]Cr bonded unit.

Exploration of composition space in templated uranium sulfates.

The phase stability of organically templated uranium sulfates in the [UO(2)(CH(3)CO(2))(2).2H(2)O/homopiperazine/H(2)SO(4)] and [UO(2)(CH(3)CO(2))(2).2H(2)O/N,N-dimethylethylenediamine/H(2)SO(4)] systems has been studied using composition space.

[(Th2F5)(NC7H5O4)2(H2O)][NO3]: an actinide-organic open framework.

We believe [(Th2F5)(NC7H5O4)2(H2O)][NO3] is the first three-dimensionally connected, actinide-organic framework solid. The structure is composed of thorium oxyfluoride chains, each of which connected to pyridinedicarboxylate groups to give a 3D cross-linked network with cavities containing nitrate anions.

Controlled structural variations in templated uranium sulfates.

A series of experiments in the UO(2)(CH(3)CO(2))(2).2H(2)O/H(2)SO(4)/1-(2-aminoethyl)piperazine/H(2)O system were conducted to determine the effects of variation in initial reactant concentrations on the reaction products. Several reaction gels were produced, in which the composition varied from 16:80:4:500 UO(2)(CH(3)CO(2))(2).