Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes

The synthesis of nanographenes (NGs) with open-shell ground states have recently attained increasing attention in view of their interesting physicochemical properties and great prospects in manifold applications as suitable materials within the rising field of carbon-based magnetism. A potential route to induce magnetism in NGs is the introduction of structural defects, for instance non-benzenoid rings, in their honeycomb lattice. Here, we report the on-surface synthesis of three open-shell non-benzenoid NGs (A1, A2 and A3) on the Au(111) surface. A1 and A2 contain two five- and one seven-membered rings within their benzenoid backbone, while A3 incorporates one five-membered ring. Their structures and electronic properties have been investigated by means of scanning tunneling microscopy, noncontact atomic force microscopy and scanning tunneling spectroscopy complemented with theoretical calculations. Our results provide access to open-shell NGs with a combination of non-benzenoid topologies previously precluded by conventional synthetic procedures.

Isolated Neutral [4]Helicene Radical Provides Insight into Consecutive Two-Photon Excitation Photocatalysis

Direct activation of strong bonds in readily available, benchtop substrates offer a straightforward simplification, albeit in most cases existing catalytic systems are limited to unlock such activation. In recent years, a surge of in-situ generated organic radicals that can act as potent photoinduced electron transfer (PET) agents have proved to be a powerful manifold for the activation of remarkably stable bonds. Herein we document the use of N,N′-di-n-propyl-1,13-dimethoxyquinacridine (nPr-DMQA•), an isolated and stable neutral helicene radical, as a highly photoreducing species. This isolable doublet state open shell radical offers a unique opportunity to shed light on the mechanism behind PET reactions of organic radicals. Experimental and spectroscopic studies revealed that this doublet radical has a long lifetime of 4.6 ± 0.2 ns, an estimated excited state oxidation potential of -3.31 V vs SCE, and can undergoes PET with organic substrates. The strongly photoreducing nature of the nPr-DMQA• was experimentally confirmed by the demonstration of photo activation of electron rich aryl bromides and chlorides. We further demonstrated that nPr-DMQA• can be photochemically generated from its cation analog (nPr-DMQA+) allowing catalytic functionalization of aryl halide via a consecutive photoexcitation mechanism (ConPET). Dehalogenation, photo-Arbuzov, photo-borylation and C-C bond formation reactions with aryl chlorides and bromides are reported herein, as well as the α-arylation of carbonyl using cyclic ketones. The latter transformation exhibits the facile synthesis of α-arylated cyclic ketones as critical feedstock chemical for diverse useful molecules, especially in the biomedical enterprises.

post-Spin Crossing Dynamics Determine the Regioselectivity in Open-shell Singlet Biradical Recombination

Radical recombination is among the fastest reactions in organic chemistry. Achieving high level of selectivities in this type of reactions is rather challenging. In a recent report on visible-light-induced dearomative...

Synthesis of the Open-Shell 3d-Transition Metal(II) Bis(phosphinidenide) [Mn{P(sIDipp)}2]

The synthesis and characterization of the first homoleptic open-shell transition metal phosphinidenide is presented. By reacting [MnL2] (L = −N(SiMe3)2) with [(sIDipp)PK] (sIDipp = 1,3-bis(2,6-di-iso-propylphenyl)-imidazolidine-2-ylidene), the formation of [Mn{P(sIDipp)}2] instead...

ADG: automated generation and evaluation of many-body diagrams

The goal of the present paper is twofold. First, a novel expansion many-body method applicable to superfluid open-shell nuclei, the so-called Bogoliubov in-medium similarity renormalization group (BIMSRG) theory, is formulated. This generalization of standard single-reference IMSRG theory for closed-shell systems parallels the recent extensions of coupled cluster, self-consistent Green’s function or many-body perturbation theory. Within the realm of IMSRG theories, BIMSRG provides an interesting alternative to the already existing multi-reference IMSRG (MR-IMSRG) method applicable to open-shell nuclei. The algebraic equations for low-order approximations, i.e., BIMSRG(1) and BIMSRG(2), can be derived manually without much difficulty. However, such a methodology becomes already impractical and error prone for the derivation of the BIMSRG(3) equations, which are eventually needed to reach high accuracy. Based on a diagrammatic formulation of BIMSRG theory, the second objective of the present paper is thus to describe the third version (v3.0) of the code that automatically (1) generates all valid BIMSRG(n) diagrams and (2) evaluates their algebraic expressions in a matter of seconds. This is achieved in such a way that equations can easily be retrieved for both the flow equation and the Magnus expansion formulations of BIMSRG. Expanding on this work, the first future objective is to numerically implement BIMSRG(2) (eventually BIMSRG(3)) equations and perform ab initio calculations of mid-mass open-shell nuclei.