All are aromatic: A 3D globally aromatic cage containing five types of 2D aromatic macrocycles

•A fully ?-conjugated molecular cage was synthesized in a simple way•Chemical oxidation led to 3D globally aromatic cage•All five types of 2D macrocycles along the skeleton are Hückel aromatic•A close relation between ?-aromaticity and established Aromaticity is vital concept organic chemistry ?-/?-conjugated molecules have intrinsic tendency become via electron delocalization. Although there been many studies on aromaticity macrocycles, examples systems very limited. Research will not only help us better understand fundamental chemical principles but also provide new type for electronics, spintronics, quantum information. In this work, 4-fold symmetric 1 facilely two-electron 12+. Our detailed experimental measurements theoretical analysis reveal that all formally available 12+ aromatic. This work discloses correlation global aromaticity. 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Indeed, our its dication (12+) shows desired More importantly, formed arms fragments including article, characterization, Ni(COD)2-mediated intermolecular Yamamoto coupling intermediate 6, followed oxidative dehydrogenation isolated octahydro-cage 7 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) dichloromethane (DCM) key 6 prepared reaction sequence involving formylation, Alder-Longo condensation, nickel (II) ion insertion starting 3. During reaction, intramolecularly coupled product 8 obtained, subsequent gave 2, serve bulky 4-tert-butyl-2,6-dimethylphenyl groups attached onto most reactive methylene sites. Thus, final products soluble stable purified routine silica gel column chromatography. voltammogram differential pulse show reversible waves half-wave potential (E1/2ox) 0.01, 0.41, 1.02 V, reduction (E1/2red) ?1.40, ?1.67, ?1.86 V (versus Fc+/Fc; Fc: ferrocene) (Figure 1A). Compound exhibits amphoteric redox behavior, (E1/2ox ?0.09, 0.28, 0.45 V) wave (E1/2red ?1.44 1B). oxidant NO·SbF6 corresponding dications 22+ (see evolution spectra during titration: Figures S1 S2), single-crystal form. No higher-oxidation-state species obtained even excessive added. DCM intense Soret band maximum (?abs) 425 nm, typical porphyrin, another ?abs 545 reminiscent quinoidal bithiophene moieties 1C), indicating well conjugated. displays broad near-infrared (NIR) region extending beyond 1,600 effective ?-electron existence 683 nm implies character. similar 1, lowest-energy split, presumably due rigid 1D). NIR (?abs 1,068 nm). crystallographic single 100 K slant center 2A). remain nearly aligned parallel other, plane-to-plane distance 7.8 Å. sulfur middle inside cavity, opposite 16.95/17.43 Å, represent inner diameter 1. distortional angles neighboring 58.8°, 62.3°, 77.5°, 89.2°, implying weak ?-conjugation them. evident 1H NMR spectrum CDCl3 298 3A). resonance ?-H (proton e) unit appears shift ? 8.83 ppm, porphyrin. resonances (protons b) appear doublets 7.00 6.33 respectively, structure. protons c d directly broadened 6.54 7.02 slow dynamic rotation previously analogous system.55Ren Park I.H. 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Graph. 14: 27Google Scholar,59Lu Multiwfn: multifunctional wavefunction analyzer.J. Comput. 33: 580-592Google ACID plot clockwise diatropic circuit field perpendicular plane (along y axis) 4A), plots directed x z do obvious flow S12 S13). NICSiso geometric calculated ?4.0 ppm. ICSS map major environment above below 4B S46). calculations suggest contains aromatic, consistent data. measured dramatic change 2B). molecule has symmetry, rotational axis across Ni(II) centers. ?, ?, ??, ?? (? equivalent ?? ? ??) facilitate discussion. Both now adopt saddle-shaped conformation, meso-carbons bent “up-down-up-down” mode relative mean plane. downward ?/??, upward connect ?/??. Overall, distorted (?/??) down (?/??) up. Such somewhat releases strain facilitates quality data does reliable bond length analysis, (67.2°, 44.9°, 72.2°, 44.2°) smaller ?-orbital overlap. separated, 10.3 At meanwhile, lateral cavity (16.36 16.40 Å) defined becomes smaller. Unlike sets well-resolved signals accordance halves separated points 3B; see S6 S7 assignment COSY (correlated apectroscopy) ROESY (rotating frame Overhause effect spectroscopy) spectra). backbone low (? 7.37 ? 9.03 ppm) ten doublet peaks, particular, a/a', b/b', c/c?, d/d' considerably shifted downfield shifts correlated shielding/de-shielding environments, assuming whole solution. clearly shown frontier orbital profiles S51). Calculations insight Interestingly, (z, x, y, xz, ?xz) cross 4A). That means, NICS(0) value ?9.52 NICS scan negative values (Table S1), demonstrates magnetically shielded S47), supporting unique system, dissected a/b/c/d a'/b'/c'/d' bottom 5), 2B, top). Then, defined: (1) ?/?? ?'/? (i.e., a-?-a?-?' c-??-c?-?); (2) ?/? ?'/?' b-?-b?-? d-??-d?-?'); (3) a-b-c-d a'-b?-c?-d'); (4) ?/?' b-c-??-c?-b?-?, b-c-??-d?-a?-?, a-d-??-d?-a?-?, a-d-??-c?-b?-?); (5) ?/?' a-b-?-b'-a'-??, a-b-?-c'-d'-??, c-d-??-d?-c?-?, c-d-??-a?-b?-?). Notably, calculations, draw conjugation pathway 46, 18, 54, 54 ?-electrons, respectively S38 S39). These canonical forms resonate form system positive charges dimensions S50). harmonic oscillator measure (HOMA) based optimized geometries increase (0.52 0.58) (0.64 0.68) I, II, IV, pathways S41 S42), HOMA (0.77) character dicationic (type III) forms. total 114 ? (excluding atoms, contribute plots) fullerenes; thus, previous symmetric, c-T126+,17Yoon bridge head carbons any actually seems attain cages, should analogs replaced non-conjugated hydrogenated linker conducted, remaining parts S22–S35). finding supports 2. slightly core, fused earring-like toward side plane, depth 2.0 Å 2C). neighbored 53.4°, 66.8°, 67.2°, respectively. Upon dication, (depth: ?3.3 Å), (29.2°, 33.3°, 43.7°, 52.4°), 2D). central non-aromatic, earrings 2.5 arisen de-shielding nearby rings. 4B). outer periphery suggests superposition [22] [18]annulene-like pathway, S40). cancelation bridges (herein, shared earrings) overall periphery, anthracene molecule. enhancement S43 S44). earring centers ?5.9 non-aromaticity cycles experiment. 3C) appearing 9.36 8.62 ppm f, respectively). thiophenes 6.78 7.60 d, respectively), non-aromatic 6.57 6.12 b, g h aryl substituents 7.18, 7.14 ppm), timescale f 10.20 9.10 b 8.55 units, 7.72, 7.63 periphery. 8.79 current. Nevertheless, environment, reasons: aromatic; non-planar far 2D); S50), results decreased density. noted coalesced room temperature, likely restricted rotation, character, nm. summary, facile strategy. local (12+). Importantly, constructional study, together c-T126+, strongly drawn skeleton. scenario again principle, is, state. obviously Continuous searching needed answer