Dehydro[12]- and -[18]annulenes fused with tetrafluorobenzene: synthesis,electronic properties,packing structures,and reactivity in the solid state

Dehydro[12]- and -[18]annulenes 3 and 4 fused with tetrafluorobenzene were newly synthesized by the copper-mediated oxidative coupling of 1,2-diethynyltetrafluorobenzene. The UV-vis spectra of 3 and 4 showed the maximum absorption to be almost identical to that of the corresponding unsubstituted benzodehydro[12]- and -[18]annulenes 1 and 2, respectively, while the reduction waves in cyclic voltammetry observed at potentials of -1.48 and -1.56 V vs Fc/Fc(+) for 3 and 4 were less negative than those for 1 and 2. In agreement with these results, theoretical calculations (B3LYP/6-31G(d)) indicated that the HOMO-LUMO gap is similar for 1 and 3 and for 2 and 4 but that the LUMO levels of 3 and 4 are apparently lowered by the electronegative fluorine substituents. The X-ray crystallography of single crystals grown from 3 (crystal A), 3.C(6)H(6) (crystal B), and a mixture of 1 and 3 (crystal C) demonstrated that the molecules of 3 are stacked in a slanted manner in crystals A and B, while those of 1 and 3 form sandwichlike 1:2 complexes (3.1.3) that are stacked in a columnar arrangement in crystal C. Despite the suitable packing for topochemical polymerization, crystals A-C were quite stable against photochemical reaction. In contrast, differential scanning calorimetry showed that the thermal polymerization occurred explosively at 120-135 degrees C.     

1,2-Didehydro[10]annulenes: structures, aromaticity, and cyclizations

The conformational space of C(10)H(8) 1,2-didehydro[10]annulenes, along with their unimolecular conversion to isonaphthalenes (cyclic allenes), has been studied computationally using DFT (B3LYP), single-reference [CCSD(T)], and multireference (MCQDPT2) post-HF methods. The introduction of the linear alkynyl moiety releases enough angle strain to make a nearly planar "heart" aromatic form the preferred conformer by more than 6 kcal/mol [CCSD(T)] over a localized C(2) "twist" structure, as opposed to the closely related C(10)H(10) [10]annulene system. Computations also show that electrocyclic ring-opening of isonaphthalenes to the heart C(10)H(8) annulene takes place through a low barrier of 15 kcal/mol, and this should be considered the working mechanism for the reported isomerizations during dehydro Diels-Alder reactions of phenylacetylenes.     

Donors and acceptors based on triangular dehydrobenzo[12]annulenes: formation of a triple-layered rosette structure by a charge-transfer complex

We present here the results of studies of the synthesis and properties of donors and acceptors based on triangular dehydrobenzo[12]annulene ([12]DBA) system as a pi core. These studies were aimed at controlling the supramolecular crystal structure. Toward this end, the tricyano[12]DBA 2 and dodecafluoro[12]DBA ( 3) were synthesized as acceptors (A) and the tris(dialkylamino)[12]DBAs 4a-d as donors (D), and their electronic properties were determined by electronic absorption spectroscopy and electrochemical measurements. The main focus, though, was the formation of supramolecular structures in crystals. These compounds form distinct packing patterns as a result of the different intermolecular interactions. Tricyano[12]DBA 2 forms a two-dimensional (2D) sheet structure via hydrogen-bonding interactions, whereas a tilted-stack structure was found for 3 because of the lack of significant intermolecular interactions. Tris(dibutylamino)[12]DBA 4b exhibits a ladder-type 2D structure, probably because of van der Waals interactions between the butyl groups. The most significant finding is that charge-transfer interactions between donor 4a and acceptor 3 combined with their triangular molecular shapes and lateral CH...F hydrogen bonding result in the formation of a 2D rosette structure consisting of two different trimeric (DAD- and ADA-type) sandwich structures with 1:2 and 2:1 A/D ratios, respectively.     

Benzannelated annulenes -12. : Theoretical study of geometries and 1H chemical shifts of benzannelated [14] annulenes

The geometries and the ¹H chemical shifts of dihydropyrene $\text{1}$ and its benzannelated derivatives $\text{2}$–$\text{8}$ have been studied by means of semiempirical quantum chemical procedures. The calculated bond lengths of $\text{1}$ and proton shifts of $\text{1}$ – $\text{5}$ are in good accord with the corresponding experimental values. We show that monobenzannelation in $\text{2}$ – $\text{4}$ causes considerable bond length alternation in the [14] perimeter and hence reduced diatropocity. The same is true for the phenanth-fused dibenzannelated compounds $\text{4}$ and $\text{7}$. On the other hand we report evidence that anth-fused dibenzannelated dihydropyrenes $\text{5}$, $\text{6}$, and $\text{8}$ should be characterized by symmetric geometrical structures without significant bond length alternation thus leading to enhanced diatropicity.     

Macrocyclic Tetraethynylethene Molecular Scaffolding: Perethynylated aromatic dodecadehydro[18]annulenes,antiaromatic octadehydro[12]annulenes,and expanded radialenes

Tetraethynylethene (3,4-diethynylhex-3-ene-1,5-diyne) molecular scaffolding provided access to novel macrocyclic nanometer-sized C-rich molecules with unusual structural and electronic properties. Starting from cis-bis-deprotected cis-bis(trialkylsilyl)protected tetraethynylethenes, the per(silylethynyl)ated octadehydro[12]annulenes 1 and 2 and the corresponding dodecadehydro[18]annulenes 4 and 5 were prepared by oxidative Hay coupling. X-Ray crystal-structure analyses of (i-Pr)₃Si-protected 2 and Me₃Si-protected 4 showed that both annulene perimeters are perfectly planar. Electronic absorption spectral comparisons provided strong evidence that the macro rings in the deep-purple-colored 1 and 2 are antiaromatic (4n π-electrons), whereas those in yellow 4 and 5 are aromatic ((4n + 2) π-electrons). Although unstable in solution, the antiaromatic compound 2 gave high-melting crystals in which the individual octadehydro[12]annulene chromophores are isolated and stabilized in a matrix-type environment formed by the bulky (i-Pr)₃Si groups. Electrochemical studies demonstrated that the antiaromatic octadehydro[12]annulene 2 undergoes two stepwise one-electron reductions more readily that the aromatic chromophore 5 . This redox behavior is best explained by the formation of an aromatic (4n + 2) π-electron dianion from 2 , whereas 5 loses its aromaticity upon reduction. The Me₃Si derivative 4 was deprotected with borax in MeOH/THF to give the highly unstable hexaethynyl-dodecadehydro[18]annulene 6 , a C₃₀H₆ isomer and macrocyclic precursor to a two-dimensional all-C-network. Deprotection of 2 did not give isolable amounts of tetraethynyl-octadehydro[12]annulene 3 due to the extreme instability of the latter. Starting from dimeric and trimeric acyclic tetraethynylethene oligomers, a series of expanded radialenes were obtained. They possess large C-cores with silylethynyl-protected peripheral valences and can be viewed as persilylated C₄₀ ( 7 ), C₅₀ ( 8 ), and C₆₀ ( 9 ) isomers. These expanded C-sheets are high-melting, highly stable, soluble materials which were readily characterized by laser-desorption time-of-flight (LD-TOF) mass spectrometry. Due to inefficient macrocyclic cross-conjugation and/or non-planarity, the extent of π-electron delocalization in 7 – 9 is limited to the longest linearly conjugated π-electron fragment. In agreement with these properties, all three expanded radialenes exhibited similar redox behavior; they are difficult to oxidize but undergo several reversible one-electron reductions in similar potential ranges. Presumably, the reduced π-electron delocalization is also at the origin of the particularly high stability of 7 – 9 .     

Dehydro[12]annulenes: structures, energetics, and dynamic processes

Density functional and coupled cluster calculations on neutral monodehydro[12]annulenes (C(12)H(10)) reveal a global minimum that should be kinetically stable. At the CCSD(T)/cc-pVDZ//BHLYP/6-31G* level, the unsymmetrical CTCTC conformer 1a lies at least 3 kcal/mol below all other isomers studied. The two isomers closest in energy to 1a are Mo?bius structure 5a (CCTCC) and all-cis 6a. Isomer 1a can undergo conformational automerization with E(a) = 3.9 kcal/mol, implying that this process would be rapid on the NMR time scale, and computed (1)H NMR parameters (GIAO-B3LYP/6-311+G**//RHF/6-31G*) are presented. Cumulenic dehydro[12]annulene isomers, with 1,2,3-butatriene subunits, were found to be reactive intermediates in the interconversion of different configurations of the alkyne forms. Pathways for configuration change of 1a, and for subsequent rearrangement to biphenyl, were investigated. The 28 kcal/mol overall barrier for the lowest energy pathway connecting 1a to biphenyl suggests that 1a is kinetically stable with respect to valence isomerization.     

Synthesis and Characterization of Dirhenadehydro[12]annulenes

The 12‐membered‐ring metallacycles [mer‐Re{≡CCH=C(R)C≡C?}Cl(PMe₂Ph)₃)]₂ (R=CMe₃, 1‐adamantyl), which are organometallic analogues of antiaromatic octadehydro[12]annulene, are prepared by heating the methyl carbyne complexes mer‐Re{≡CCH=C(R)C≡CH}(CH₃)Cl(PMe₂Ph)₃. An intermolecular σ‐bond metathesis between the Re?CH₃ bond and the acetylenic C?H bond is proposed for their formation.     

Benzannelated [9] and [13] annulenes: Formation,structural properties and the effect of benzannelation on the aromaticity of the (4n+2) π anionic sy

The synthesis of benzannelated [9] and [13] annulenenes is described, 1,2:3,4-dibenzocyclononatetraene 3 and its diphenyl derivative 10 show upon deprotonation the initial formation of a non-planar partially delocalized anions 4 and 11 respectively, which undergo into the planar aromatic-diatropic dibenzocyclononatetraenyl anions 4a and 12. The immediate formation of the aromatic 1,2:5,6 - dibenzocyclononatetraenyl anion 14 upon deprotonation of 1,2:5,6 - dibenzocyclononatetraene 13 precludes peri H-H repulsions in the aromaticity development of the dibenzocyclononatetraenyl anions. The deprotonation of tetrabenzo[13]annulene 15 afforded anion 17, which shows reduced diatropic character as compared with non-benzannelated[13] annulenyl anion. The spatial arrangement of 17 is discussed.     

Competing isomerizations of [12]annulenes: Diels-Alder reaction versus electrocyclization

Experimentally, tri-trans-[12]annulene and tris(cyclohexeno)[12]annulene exhibit differing reactivities. Whereas the former, after isomerizing to its di-trans isomer, undergoes sequential electrocyclizations, the latter follows a Diels-Alder pathway after initial electrocyclization. B3PW91/6-31+G*//B3LYP/6-31G* calculations indicate that cyclohexenofusion simultaneously hinders the second electrocyclization and facilitates Diels-Alder reaction, primarily by inducing greater puckering in the intermediate eight-membered ring.     

Theoretical study of stability, structures, and aromaticity of multiply N-confused porphyrins.

The total electronic energy and nucleus-independent chemical shift (NICS) of 95 isomers of N-confused porphyrin (NCP: normal porphyrin (N(0)CP), singly N-confused porphyrin (N(1)CP), doubly N-confused porphyrin (N(2)CP), triply N-confused porphyrin (N(3)CP), and fully N-confused porphyrin (N(4)CP)) have been calculated by the density functional theory (DFT) method. The stability of NCP decreased by increasing the number of confused pyrrole rings. Namely, the relative energies of the most stable isomers in each confusion level increased in a stepwise manner approximately by +18 kcal/mol: 0 (N(0)CP1), +17.147 (N(1)CP2), +37.461 (N(2)CPb3), +54.031 (N(3)CPd6), and +65.636 kcal/mol (N(4)CPc8). In this order, the mean plane deviation of these isomers increased from 0.000 to 0.123, 0.170, 0.215, and 0.251 A, respectively. The unusual tautomeric forms of pyrrole ring with an sp(3)-carbon were found in the stable forms of N(3)CP and N(4)CP. The NICS values at the mean position of the 24 core atoms were nearly the same for the most aromatic isomers regardless of the confusion level: -15.1280 (N(0)CP1), -13.8493 (N(1)CP2), -13.7267 (N(2)CPd1), -11.7723 (N(3)CPb5), and -13.6224 ppm (N(4)CPa6). The positive correlation between aromaticity and stability was inferred from the plots of NICS and the relative energy of NCP for N(0)CP, N(1)CP, and trans-N(2)CP. On the other hand, the correlation was negative for cis-N(2)CP, N(3)CP, and N(4)CP isomers.     

苯并咪唑苯并异喹啉酮及其衍生物的电子结构和光谱性质的理论研究

采用密度泛函、含时密度泛函和单激发组态相互作用(CIS)方法研究了苯并咪唑苯并异喹啉酮(1)及其衍生物的电子结构特性和光谱性质,并用极化连续模型考虑了溶剂的影响.结果表明,化合物1及其衍生物的吸收和荧光发射过程的电子垂直跃迁是由于分子内的电荷迁移.化合物1中取代基的位置及给吸电子能力影响其HOMO-LUMO能隙和电荷迁移量.在分子中引入吸电子和给电子取代基,均使最大吸收波长和最大荧光发射波长红移,计算的结果与实验结果吻合得较好.     

两种C~6~0双炔衍生物的结构、光谱和二阶非线性光学性质的 理论研究

用INDO/2和INDO/SCI方法,计算了C~6~0C(C=CH)~2基态电子结构和电子光谱,所得结果与实验结果基本一致.在此基础上,设计了C60(C=CH)~2,并用同样方法计算了电子结构和光谱.在正确的电子光谱基础上,用ZINDO-SOS方法计算了2个分子的二阶非线性光学系数β~i~j~k和β~μ,并对其结果进行了分析和讨论.结论是,乙炔基与C~6~0(C=CH)~2有更大的非线性光学系数,是有希望的非线性光学备选材料分子。     

Superstructure-dependent optical and electrical properties of an unusual face-to-face, pi-stacked, one-dimensional assembly of dehydrobenzo[12]annulene in the crystalline state

To develop a novel pi-conjugated molecule-based supramolecular assembly, we designed and synthesized trisdehydrotribenzo[12]annulene ([12]DBA) derivative 2 with three carboxyl groups at the periphery. Recrystallization of 2 from DMSO gave a crystal of the solvate 23 DMSO. Crystallographic analysis revealed, to our surprise, that a face-to-face pi-stacked one-dimensional (1D) assembly of 2 was achieved and that the DMSO molecule played a significant role as a "structure-dominant element" in the crystal. This is the first example of [12]DBA to stack completely orthogonal to the columnar axis. To reveal its superstructure-dependent optical and electrical properties, 2 and its parent molecule 1, which crystallizes in a herringbone fashion, were subjected to fluorescence spectroscopic analysis and charge-carrier mobility measurements in crystalline states. The 1D stacked structure of 2 provides a red-shifted, broadened, weakened fluorescence profile (lambda(max) = 545 nm, phi(F) = 0.01), compared to 1 (lambda(max) = 491 nm, phi(F) = 0.12), due to strong interactions between the p orbitals of the stacked molecules. The charge-carrier mobility of the single crystal of 23 DMSO, as well as 1, was determined by flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements. The single crystal of 23 DMSO revealed significantly-anisotropic charge mobility (sigma(mu) = 1.5x10(-1) cm(2) V(-1) s(-1)) along the columnar axis (crystallographic c axis). This value is 12 times larger than that along the orthogonal axis (the a axis).     

Syntheses and Properties of Graphyne Fragments: Trigonally Expanded Dehydrobenzo[12]annulenes

We present herein the synthesis and properties of the largest hitherto unknown graphyne fragment, namely trigonally expanded tetrakis(dehydrobenzo[12]annulene)s (tetrakis‐DBAs). Intramolecular three‐fold alkyne metathesis reactions of hexakis(arylethynyl)DBAs 9 a and 9 b using Fürstner’s Mo catalyst furnished tetrakis‐DBAs 8 a and 8 b substituted with tert‐butyl or branched alkyl ester groups in moderate and fair yields, respectively, demonstrating that the metathesis reaction of this protocol is a powerful tool for the construction of graphyne fragment backbones. For comparison, hexakis(arylethynyl)DBAs 9 c – g have also been prepared. The one‐photon absorption spectrum of tetrakis‐DBA 8 a bearing tert‐butyl groups revealed a remarkable bathochromic shift of the absorption cut‐off (λ_cutoff) compared with those of previously reported graphyne fragments due to extended π‐conjugation. Moreover, in the two‐photon absorption spectrum, 8 a showed a large cross‐section for a pure hydrocarbon because of the planar para‐phenylene‐ethynylene conjugation pathways. Hexakis(arylethynyl)‐DBAs 9 c – e and 9 g and tetrakis‐DBA 8 b bearing electron‐withdrawing groups aggregated in chloroform solutions. Comparison between the free energies of 9 e and 8 b bearing the same substituents revealed the more favorable association of the latter due to stronger π–π interactions between the extended π‐cores. Polarized optical microscopy observations, DSC, and XRD measurements showed that 8 b and 9 e with branched alkyl ester groups displayed columnar rectangular mesophases. By the time‐resolved microwave conductivity method, the columnar rectangular phase of 8 b was shown to exhibit a moderate charge‐carrier mobility of 0.12 cm² V^?1 s^?1. These results indicate that large graphyne fragments can serve as good organic semiconductors.     

Novel thiophene-substituted tetrathia[22]annulenes[2,1,2,1]: synthesis,physical properties,and improvement in field-effect behavior

Novel conjugated macrocycles, thiophene-substituting tetrathia[22]annulenes[2,1,2,1] (TTAs, and 5b), were synthesized through a convenient four-step procedure. They were evidenced to have high aromaticity by NMR, UV–vis absorption spectra, and calculation. Their UV–vis absorption spectra, thermal stability, electrochemical properties, thin film morphology were studied and the field-effect transistors based on 5a and 5b through a vapor deposition method performed good with reproducible bulk-like carrier mobilities (as high as 0.53 cm² V⁻¹ S⁻¹) and high on/off ratios (as high as 9.0×10⁵), which was among the best records in this series.     

Generation and characterization of highly strained dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes

To generate dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes ([12]- and [14]DBAs) having a highly deformed triyne moiety, [4.3.2]propellatriene-anneleted dehydro[12]- and dehydro[14]annulenes were prepared as their precursors. UV irradiation of the precursors resulted in the photochemical [2 + 2] cycloreversion to generate the strained [12]- and [14]DBAs, respectively. The [12]DBA was not detected by 1H NMR spectroscopy, but it was intercepted as Diels-Alder adducts in solution, suggesting its intermediacy. Its spectroscopic characterization was successfully carried out by UV-vis spectroscopy in a 2-methyltetrahydrofuran (MTHF) glass matrix at 77 K and by FT-IR spectroscopy in an argon matrix at 20 K. On the other hand, the [14]DBA was stable enough for observation by 1H and 13C NMR spectra in solution, though it was not isolated because of the low efficiency of the cycloreversion. The [14]DBA was also characterized by interception as Diels-Alder adducts in solution and by UV-vis spectroscopy in a MTHF glass matrix at 77 K. The kinetic stabilities of the DBAs are compared with the related dehydrobenzoannulenes with respect to the topology of the pi-systems. In addition, the tropicity of the [14]DBA is discussed based on its experimental and theoretical 1H NMR chemical shifts.     

Theoretical investigation into the structural, thermochemical, and electronic properties of the decathio[10]circulene

For the first time, a theoretical study has been performed on the prototypical decathio[10]circulene (C(20)S(10)) species, which is an analogue of the novel octathio[8]circulene "Sulflower" molecule (C(16)S(8)). Examinations of the singlet and triplet states of C(20)S(10) were made at the B3LYP/6-311G(d) level. Local minima of C(2) and C(s) symmetry were found for the lowest singlet and triplet states, respectively. The stability of C(20)S(10) was assessed by calculating the ΔH°(f) of C(16)S(8) and C(20)S(10) and the ΔH(o) for their decomposition into C(2)S units. Frontier molecular orbital plots show that structural adjacent steric factors along with the twist and strain orientations of C(20)S(10) do not disturb the aromatic π-delocalizing effects. In fact, C(20)S(10) maintains the same p(z) HOMO character as C(16)S(8). These similarities are further verified by density-of-states characterization. Calculated infrared spectra of C(16)S(8) and C(20)S(10) show broad similarities. Molecular electrostatic potential results reveal that eight of the peripheral sulfur atoms are the most electronegative atoms in the molecule, while the interior ten-membered ring exhibits virtually no electronegativity.     

硫化反式聚异戊二烯电子性质的理论化学研究

应用量子化学计算方法,对反式聚异戊二烯本征态和硫化态结构的能量及电子性质等进行了计算.结果表明,当聚异戊二烯掺杂硫后,相邻两链之间的距离a⊥变窄,体系的总能量降低,从而使整个掺杂体系更加稳定.另外,在硫化聚异戊二烯分子中,S原子位于两个相邻聚异戊二烯链之间,并偏向于其中一个分子链的C C双键的一侧,即与相邻两链中相对应的两个C C双键形成π-p-π共轭体系,增加了电子在两个聚异戊二烯链间的流动性,从而使硫化的反式聚异戊二烯更加稳定.另外,根据固体能带理论,采用量子化学EHMO方法,对反式聚异戊二烯本征态和硫掺杂态的能带结构进行了计算,根据硫化前后能隙和带宽的变化,解释了反式聚异戊二烯掺杂后呈现电导率各向异性的原因.     

Synthesis and properties of p-benzoquinone-fused hexadehydro[18]annulenes

A series of hexadehydro[18]annulenes fused with different numbers of p-benzoquinone, 4-6, were synthesized by stepwise transformation of the p-dimethoxybenzene moiety of the precursor dehydroannulene 3 fused with three 3,6-dimethoxy-4,5-dimethylbenzene units at 1,2-positions into p-benzoquinone using ceric ammonium nitrate. The UV-vis spectra of compounds 4 and 5, which have both electron-donating p-dimethoxybenzene unit(s) and electron-accepting p-benzoquinone unit(s) in the π-systems, showed the maximum absorption bands bathochromically shifted in comparison with 3 having only p-dimethoxybenzene units and 6 having only p-benzoquinone units. However, the solvatochromism expected for 4 and 5 was found to be quite weak possibly because the HOMO and LUMO (B3LYP/6-31G(d)) are not localized but rather delocalized over the whole π-systems.