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1. Electron transport in a sequentially doped naphthalene diimide polymer

   https://doi.org/10.1039/d0ma00406e  

   Al Kurdi, Khaled; Gregory, Shawn A.; Jhulki, Samik; Conte, Maxwell; Barlow, Stephen; Yee, Shannon K.; Marder, Seth R. (September 2020, Materials Advances)

   null (Ed.)

   The effects of sequential n-doping on a high-electron-mobility naphthalene-diimide-based copolymer poly[( N , N ′-bis(2-decyltetradecyl)-naphthalene-1,8:4,5-bis(dicarboximide)-2,6-diyl)-(selenophene-2,5-diyl)-(benzo[ c ][1,2,5]thiadiazole-4,7-diyl)-(selenophene-2,5-diyl)], PNBS, are reported. Grazing-incidence XRD measurements show that PNBS doped with 2,2′-bis(4-(dimethylamino)phenyl)-1,1′,3,3′-tetramethyl-2,2′,3,3′-tetrahydro-1 H ,1′ H -2,2′-bibenzo[ d ]imidazole, (N-DMBI) 2 , has increased order relative to both the pristine polymer and a film doped with ruthenium pentamethylcyclopentadienyl mesitylene dimer. Films of PNBS optimally doped with (N-DMBI) 2 show electrical conductivities approaching 2 mS cm −1 in air. Temperature-dependent electrical measurements suggest that the polaronic charge carriers are highly localized, which is consistent with the moderate conductivity values obtained. 

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2. Formation of Stilbene Azo‐Dimer by Direct Irradiation of p‐Azidostilbene ^†

   https://doi.org/10.1111/php.13659  

   Osisioma, Onyinye; Patton, Leanna J.; Merugu, Rajkumar; Govorov, Dmitrii; Milbrandt, Margaret A.; Jarus, Cassandra; Karney, William L.; Gudmundsdottir, Anna D. (July 2022, Photochemistry and Photobiology)

   ABSTRACT Triplet arylnitrenes may provide direct access to aryl azo‐dimers, which have broad commercial applicability. Herein, the photolysis ofp‐azidostilbene (1) in argon‐saturated methanol yielded stilbene azo‐dimer (2) through the dimerization of tripletp‐nitrenostilbene (³1N). The formation of³1Nwas verified by electron paramagnetic resonance spectroscopy and absorption spectroscopy (λ_max ~ 375 nm) in cryogenic 2‐methyltetrahydrofuran matrices. At ambient temperature, laser flash photolysis of1in methanol formed³1N(λ_max ~ 370 nm, 2.85 × 10⁷ s⁻¹). On shorter timescales, a transient absorption (λ_max ~ 390 nm) that decayed with a similar rate constant (3.11 × 10⁷ s⁻¹) was assigned to a triplet excited state (T) of1. Density functional theory calculations yielded three configurations for T of1, with the unpaired electrons on the azido (T_A) or stilbene moiety (T_Tw, twisted and T_Fl, flat). The transient was assigned to T_Twbased on its calculated spectrum. CASPT2 calculations gave a singlet–triplet energy gap of 16.6 kcal mol⁻¹for1 N; thus, intersystem crossing of¹1Nto³1Nis unlikely at ambient temperature, supporting the formation of³1Nfrom T of1. Thus, sustainable synthetic methods for aryl azo‐dimers can be developed using the visible‐light irradiation of aryl azides to form triplet arylnitrenes. 

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3. Extremely Crowded Biaryls

   https://doi.org/10.1002/ejoc.202100399  

   Du, Yuchen; Mague, Joel T.; Pascal, Jr., Robert A. (June 2021, European Journal of Organic Chemistry)

   Abstract Highly congested derivatives of biphenyl were prepared by double Diels‐Alder reactions of cyclopentadienones with substituted butadiynes. The reaction of 2,3,5‐tri(tert‐butyl)cyclopentadienone (5) and diphenylbutadiyne (3) gave only the single adduct, 1‐(phenylethynyl)‐2‐phenyl‐3,5,6‐tri‐tert‐butylbenzene (6), and even extreme conditions gave no second addition. When tetracyclone (4) was added to bis(trimethylsilyl)butadiyne (8), two additions were achieved, but one silyl group was lost either during, or immediately following, the second addition to give 2‐(trimethylsilyl)‐2′,3,3′,4,4′,5,5′,6‐octaphenylbiphenyl (11). However, when 3,4‐diphenyl‐2,5‐dimethylcyclopentadienone (12) was added to8, the fully substituted 2,2′‐bis(trimethylsilyl)‐4,4′,5,5′‐tetraphenyl‐3,3′,6,6′‐tetramethylbiphenyl (14) was formed. The X‐ray structures of compounds11and14show them to be quite crowded, but the central biphenyl rings do not exhibit the distortions previously observed in decaphenylbiphenyl. In an alternative approach, arynes were added to 5,5′‐bis(4‐chlorophenyl)‐3,3′,4,4′‐tetraphenyl‐2,2′‐bis(cyclopentadienone) (18). Simple benzyne added twice to give 4,4′‐bis(4‐chlorophenyl)‐2,2′,3,3′‐tetraphenyl‐1,1′‐binaphthyl (19) in low yield, but tetraphenylbenzyne, generated from tetraphenylanthranilic acid, added only once. 

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4. Rotation‐Inversion Isomerization of Tertiary Carbamates: Potential Energy Surface Analysis of Multi‐Paths Isomerization Using Boltzmann Statistics

   https://doi.org/10.1002/cphc.202200442  

   Jameson, Brian; Glaser, Rainer (October 2022, ChemPhysChem)

   Abstract Potential energy surface (PES) analyses at the SMD[MP2/6–311++G(d,p)] level and higher‐level energies up to MP4(fc,SDTQ) are reported for the fluorinated tertiary carbamateN‐ethyl‐N‐(2,2,2‐trifluoroethyl) methyl carbamate (VII) and its parent systemN,N‐dimethyl methyl carbamate (VI). Emphasis is placed on the analysis of the rotational barrier about the CN carbamate bond and its interplay with the hybridization of theN‐lone pair (NLP). All rotational transition state (TS) structures were found by computation of 1D relaxed rotational profiles but only 2D PES scans revealed the rotation‐inversion paths in a compelling fashion. We found four unique chiral minima ofVII, one pair each ofE‐andZ‐rotamers, and we determined theeightunique rotational TS structures associated with every possibleE/Z‐isomerization path. It is a significant finding that all TS structures featureN‐pyramidalization whereas the minima essentially contain sp²‐hybridized nitrogen. We will show that the TS stabilities are affected by the synergetic interplay between NLP/CO₂repulsion minimization, NLP→σ^*(CO) negative hyperconjugation, and two modes of intramolecular through‐space electrostatic stabilization. We demonstrate how Boltzmann statistics must be applied to determine the predicted experimental rotational barrier based on the energetics of all eight rotamerization pathways. The computed barrier forVIIis in complete agreement with the experimentally measured barrier of the very similar fluorinated carbamateN‐Boc‐N‐(2,2,2‐trifluoroethyl)‐4‐aminobutan‐1‐olII. NMR properties ofVIIwere calculated with a variety of density functional/basis set combinations and Boltzmann averaging over theE‐andZ‐rotamers at our best theoretical level results in good agreement with experimental chemical shifts δ(¹³C) andJ(¹³C,¹⁹F) coupling constants ofII(within 6 %). 

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5. Cage Match: Comparing the Anion Binding Ability of Isostructural Versus Isofunctional Pairs of Metal‐Organic Nanocages

   https://doi.org/10.1002/chem.202303013  

   Dutton, Kaitlyn G.; Jones, Taro J.; Emge, Thomas J.; Lipke, Mark C. (November 2023, Chemistry – A European Journal)

   Abstract Affinities of six anions (mesylate, acetate, trifluoroacetate,p‐toluenecarboxylate,p‐toluenesulfonate, and perfluorooctanoate) for three related Pt²⁺‐linked porphyrin nanocages were measured to probe the influence of different noncovalent recognition motifs (e. g., hydrogen bonding, electrostatics, π bonding) on anion binding. Two new hosts of M₆L₃¹²⁺(1b) and M₄L₂⁸⁺(2) composition (M=(en)Pt²⁺, L=(3‐py)₄porphyrin) were prepared in a one‐pot synthesis and allowed comparison of hosts that differ in structure while maintaining similar N−H hydrogen‐bond donor ability. Comparisons of isostructural hosts that differ in hydrogen‐bonding ability were made between1band a related M₆L₃¹²⁺nanoprism (1a, M=(tmeda)Pt²⁺) that lacks N−H groups. Considerable variation in association constants (K₁=1.6×10³ M⁻¹to 1.3×10⁸ M⁻¹) and binding mode (exovs.endo) were found for different host–guest combinations. Strongest binding was seen betweenp‐toluenecarboxylate and1b, but surprisingly, association of this guest with1awas only slightly weaker despite the absence of NH⋅⋅⋅O interactions. The high affinity betweenp‐toluenecarboxylate and1acould be turned off by protonation, and this behavior was used to toggle between the binding of this guest and the environmental pollutant perfluorooctanoate, which otherwise has a lower affinity for the host. 

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