: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Umbrella-like inversion of pyramidalized amines proceed through a planar transition state (TS). Stabilization of the TS through N(lone-pair) → σ*(C–C) “negative hyperconjugation” in diamino-o-carbo...

Transition-State-like Planar Structures for Amine Inversion with Ultralong C-C Bonds in Diamino-o-carborane and Diamino-o-dodecahedron.

Novel functional materials are urgently needed to help combat the major global challenges facing humanity, such as climate change and resource scarcity. Yet, the traditional experimental materials discovery process is slow and the material space at our disposal is too vast to effectively explore using intuition-guided experimentation alone. Most experimental materials discovery programs necessarily focus on exploring the local space of known materials, so we are not fully exploiting the enormous potential material space, where more novel materials with unique properties may exist. Computation, facilitated by improvements in open-source software and databases, as well as computer hardware has the potential to significantly accelerate the rational development of materials, but all too often is only used to postrationalize experimental observations. Thus, the true predictive power of computation, where theory leads experimentation, is not fully utilized. Here, we discuss the challenges to successful implementation of computation-driven materials discovery workflows, and then focus on the progress of the field, with a particular emphasis on the challenges to reaching novel materials.

https://pubs.acs.org/doi/pdf/10.1021/jacs.2c06833

Into the Unknown: How Computation Can Help Explore Uncharted Material Space

We report on our investigation of C-C bonding longer than 2.0 A, which can be realized by perpendicularly facing two fluorenyl rings in the title compound. A small orbital overlap between the distantly positioned carbon atoms is observed as a small concentration of electrons on the X-ray electron density map. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the compound originate from the in-phase and out-of-phase interactions of the overlapping orbitals, respectively, with a gap of 2.39 eV. Solid-state 13C NMR spectroscopy shows a sharp peak at 82.9 ppm for the long-bonded carbons, and a CASSCF(6,6) calculation indicates small diradical character. The experimental and theoretical analyses reveal sufficient covalent-bonding interaction in the long-bonded carbon pair.

Long Carbon-Carbon Bonding beyond 2 Å in Tris(9-fluorenylidene)methane.

Synthesis and properties of anthracene-based cyclic π-clusters which possess two and four anthracene units are discussed. The optimal cyclization conditions were determined based on a nickel(0)-mediated reaction that afforded a cyclic anthracene dimer as the major product. Bringing two anthracene planes in close proximity in a face-to-face manner resulted in red-shifted absorption owing to the narrowing of the HOMO-LUMO gap. The cyclic anthracene dimer exhibits multi-stimuli responsiveness due to high π-congestion. For example, photoirradiation on the anthracene dimer affords its photoisomer having C-C bonds that are longer than 1.65 A, which can undergo thermal reversion under gentle heating. This enabled mechanochromism of the photoisomer (colorless) to the original anthracene dimer (red). Photoisomerization was also observed in the crystalline state, accompanied by crystal jumping or collapsing, that is, the photosalient effect.

Synthesis of Anthracene-Based Cyclic π-Clusters and Elucidation of their Properties Originating from Congested Aromatic Planes

The synthesis of a series of 1,2-diamino-o-carboranes (1-4) is reported. The molecular structures of these diamino-o-carboranes are remarkable as the inner-cluster C-C bonds are all ultra-long (162.7-193.1 pm) and vary substantially with small variations in the substituents. The results of quantum mechanical investigations suggest that the origin of the bond elongation is significant in-plane negative hyperconjugation of lone pairs of the nitrogen substituents with the σ* orbitals of the C-C bonds in o-carboranes.

Exceptionally Long C-C Single Bonds in Diamino-o-carborane as Induced by Negative Hyperconjugation.

A new set of stereochemically diverse phosphino-oxazoline ligands derived from simple L-amino acids and 2-(diphenylphosphaneyl)benzoic acid were developed. Those mono anionic tridentated N,N,P-ligands promote the Cu-catalyzed enantioselective radical coupling of terminal alkynes with a broad range of benzylic halides including benzo-fused cyclic α-halides and α-silyl benzyl halides in high yield and excellent enantioselectivity under mild reaction conditions. With multi distinct sites for structural modification, a diverse pool of chiral N,N,P-ligands is readily accessed, allowing for rapid optimization of the ligand structure for a specific substrate. Notably, the enantioselective alkynlylation of benzylic halides bonds in benzo-cyclic molecules has also been realized for the first time. Appendix S1: Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. 

Development of Novel
 Phosphino‐Oxazoline
 Ligands and Their Application in Asymmetric Alkynlylation of Benzylic Halides

The reaction of dipotassio-tetrasilan-1,4-diide (4) with anhydrous SnCl2 at low temperature results in the formation of a five-membered cyclic potassio chlorostannate(II) ([(18-C-6)K](1)). By careful cation exchange reactions, it was transformed into the sodium chlorostannylenoid 2 (by using Na2 [B12 Cl12 ]) or into the non-stabilized cyclic bissilylstannylene 3 (through applying Li[Al(OC(CF3 )3 )4 ]). The increasing Lewis basicity of the bissilylstannylene 3 was analyzed by combined methods of DFT calculations and NMR spectroscopy and substantiated by the synthesis of the corresponding iron carbonyl complexes 7 and 8 from the chlorostannate 1 and the stannylene 3, respectively.

Cation‐Triggered Stannate(II)/Stannylenoid/Stannylene Conversion

A series of 1,2-N-substituted o-carboranes were obtained. The C–C bond lengths of secondary-amino o-carboranes 3 were compared. The relationship between C–C distances and the electron effects of the benzyl groups was discussed. DFT calculations with and without dispersion energy correction show that significant attractive dispersion forces were present, which arise from the skeletons of the o-carborane cages.

Synthesis, structure and DFT calculations of 1,2-N-substituted o-carboranes.

N-heterocyclic carbenes with a nido-C2B9 carborane backbone

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Papers

Exceptionally Long C-C Single Bonds in Diamino-o-carborane as Induced by Negative Hyperconjugation.

Development of Novel Phosphino‐Oxazoline Ligands and Their Application in Asymmetric Alkynlylation of Benzylic Halides

Cation‐Triggered Stannate(II)/Stannylenoid/Stannylene Conversion

Synthesis, structure and DFT calculations of 1,2-N-substituted o-carboranes.

N-heterocyclic carbenes with a nido-C2B9 carborane backbone