Judy I-Chia Wu

• PhD
• Professor (Assistant) at University of Houston

Self-assembling building blocks like the 4-pyridone can exhibit extraordinary H-bond-aromaticity coupling effects. Computed dissected nucleus independent chemical shifts (NICS(1)zz ), natural bond orbital (NBO) charges, and energy decomposition analyses (EDA) for a series of hydrogen (H-) bonded 4-pyridone chains (4-py)n (n = 2 to 8) reveal that H-...

Computed association energies and dissected nucleus-independent chemical shifts (NICS) document the mutual enhancement (or reduction) of intermolecular interactions and the aromaticity of H-bonded substrates. H-bonding interactions that in-crease cyclic 4n+2 π-electron delocalization boost aromaticity. Conversely, such interactions are weak-ened wh...

Rigorous quantum chemical investigations of the SN2 identity exchange reactions of methyl, ethyl, propyl, allyl, benzyl, propargyl, and acetonitrile halides (X = F-, Cl-) refute the traditional view that the acceleration of SN2 reactions for substrates with a multiple bond at Cβ (carbon adjacent to the reacting Cα center) is primarily due to π-conj...

This article emphasizes two underappreciated aspects of hyperconjugation in hydrocarbons, two-way hyperconjugation and hyperconjugation in tight spaces. Non-planar polyenes, e.g. cyclooctatetraene (D2d), biphenyl (D2), styrene (C1), the non-planar rotational transition states of planar polyenes (e.g. perpendicular 1,3-butaiene), as well as the larg...

Despite its highly nonplanar geometry, the tub-shaped D2d cyclooctatetraene (COT) minimum is far from being an unconjugated polyene model devoid of important π interactions. The warped skeleton of D2d COT results in the large stabilization (41.1 kcal/mol) revealed by its isodesmic bond separation energy (BSE). This originates largely from the “two-...

Aromaticity and antiaromaticity are pivotal concepts in chemistry, with significant implications for molecular properties and reactivity. In particular, thanks to their increased conductivity and small HOMO–LUMO energy gaps, antiaromatic molecules are promising for use in organic electronics. The inherent instability of such molecules is often addr...

The first tunable nano‐bending structures of [1]rotaxane containing a single‐fluorophoric N,N′‐diphenyl‐dihydrodibenzo[a,c]phenazine (DPAC) moiety (i.e., [1]RA) are developed as a loosened lasso structure to feature the bright white‐light emission [CIE (0.27, 0.33), Φ = 21.2%] in THF solution, where bi‐stable states of bending and twisted structure...

The lack of efficient and robust deep-blue phosphorescent metal complexes remains a significant challenge in the context of electroluminescent color displays. The emissive triplet states of blue phosphors are deactivated by low-lying metal-centered (3MC) states, which can be ameliorated by increasing the σ-donating ability of the supporting ligands...

Bistable [c2] daisy chain rotaxanes with respective extended and contracted forms of [c2]A and [c2]B containing a blue-emissive anthracene (AN) donor and orange-emissive indandione-carbazole (IC) acceptor were successfully synthesized via click reaction. Tunable-emission bistable [c2] daisy chain rotaxanes with fluorescence changes from blue to ora...

The phosphaquinolinone scaffold has been previously studied as a modular core for a variety of fluorescent species where use of substituent effects has focused on increasing or decreasing electron density in the core rings. We now report the synthesis and analysis of several pyridine‐containing phosphaquinolinone species exhibiting notable linear c...

The self-trapping nano-loop structures of [1]rotaxanes exhibited multiple Förster resonance energy transfer (FRET) OFF/ON patterns via dual and sequential locking/unlocking processes. Upon UV exposure, the pH-gated photoisomerization of dithienylethene (DTE)...

Manipulations of singlet oxygen (¹O2) generations by the integration of both aggregation‐induced emission luminogen (AIEgen) photosensitizer and photochromic moieties have diversified features in photodynamic therapy applications. Through Förster resonance energy transfer (FRET) pathway to induce red PL emissions (at 595 nm) for ¹O2 productions, [1...

A supramolecular host-guest [2]pseudo-rotaxane polymer containing blue-emissive (λem = 425 nm) anthracene-based di-topic donor guest (AN-G) and green-emissive (λem = 530 nm) napthalimide-based di-topic acceptor host (NP–H) after hydrogen sulfide (HS⁻ anion) detection in semi-aqueous media was developed in this study. Towards HS⁻ detection, the bi-f...

Novel aggregation-induced emission (AIE) polymers, i.e., P1-SP and P2-SP, consisting of AIEgenic tetraphenylethylene (TPE) and photochromic spiropyran (SP) units are reported. Both P1-SP and P2-SP exhibit excellent AIE behaviours of TPE moieties in near-aqueous solutions THF/H2O (95% water) and solid states with strong cyan and blue emissions at 49...

This year marks the 50th anniversary of Baird’s rules of aromaticity — a set of perturbational molecular orbital theory analyses that has garnered considerable attention in the past ten years in light of its many real-world applications in photochemistry.

We introduce phosphorescent platinum aryl acetylide complexes supported by tert-butyl-isocyanide and strongly σ-donating acyclic diaminocarbene (ADC) ligands. The precursor complexes cis-[Pt(CNtBu)2(C≡CAr)2] (4a-4f) are treated with diethylamine, which undergoes nucleophilic addition with one of the isocyanides to form the cis-[Pt(CNtBu)(ADC)(C≡CAr...

Inclusion of a second nitrogen atom in the aromatic core of phosphorus‐nitrogen (PN) heterocycles results in unexpected tautomerization to a nonaromatic form. This tautomerization, initially observed in the solid state through X‐ray crystallography, is also explained by computational analysis. We prepared an electron deficient analogue (2 e) with a...

Two diamond-shaped and partially fluorinated dehydrobenz[18]annulene macrocycles have been synthesized through a one-pot synthesis relying on fourfold Sonogashira coupling. Single crystal structures of the prepared macrocycles show continuous columnar stacks of these molecules that are mediated by the fluoroarene–alkyne, arene–alkyne, fluoroarene–f...

A series of bistable photo-switchable [c2] daisy chain rotaxanes containing photochromic spiropyran (SP) and triphenylamine-chalcone (TPA-C) chromophores were synthesized via the self-sorting strategy and Click reaction, which could be controlled...

Computed nucleus-independent chemical shifts (NICS), contour plots of isotropic magnetic shielding (IMS), and gauge-including magnetically induced current (GIMIC) plots suggest that polarization of the π-system of acridones may perturb the...

Many popular organic chromophores that catalyze photoinduced proton-coupled electron transfer (PCET) reactions are aromatic in the ground state but become excited-state antiaromatic in the lowest ππ* state. We show that excited-state antiaromaticity makes electron transfer easier. Two representative photoinduced electron transfer processes are inve...

A multi-stimuli responsive pseudo [3]rotaxane NI-DBC/RB-DBA was composed of a green-emissive (λem = 530 nm) naphthalimide-based macrocyclic host and a turn-on red-emissive (λem = 595 nm) rhodamine-based guest towards Fe³⁺ ion, which illustrated interesting photo-physical properties in dioxane/H2O (4:6, v/v) solutions. Due to the chelation-induced r...

p>Baird antiaromaticity plays a central role in the photochemistry of proton-coupled electron transfer (PCET) reactions. We recognize that many popular organic chromophores that catalyze photoinduced PCET reactions are Hückel aromatic in the ground state, but gain significant Baird antiaromatic character in the lowest ππ* state, having important ba...

In this paper, we report a series of six neutral, blue-phosphorescent cyclometalated iridium complexes of the type Ir(C^Y)2(CNAr)(CN). The cyclometalating ligands in these compounds (C^Y) are either aryl-substituted 1,2,4-triazole or NHC ligands, known to produce complexes with blue phosphorescence. These cyclometalating ligands are paired with π-a...

Beginning from a historical viewpoint, this chapter discusses the evolution of the antiaromaticity concept—covering the early synthetic challenges of preparing cyclobutadiene, orbital symmetry considerations of antiaromaticity, and transformations that convert [4n] π-antiaromatic rings into “aromatic” systems, ending with a brief survey of some app...

Here we report five blue‐phosphorescent platinum bis‐phenylacetylide complexes with an investigation of their photophysical and electrochemical attributes. Three of the complexes (1–3) are of the general formula cis‐Pt(CNR)2(C≡CPh)2, in which CNR is a variably substituted isocyanide and C≡CPh is phenylacetylide. These isocyanide complexes serve as...

The Watson–Crick A•T and G•C base pairs are not only electronically complementary, but also photochemically complementary. Upon UV irradiation, DNA base pairs undergo efficient excited-state deactivation through electron driven proton transfer (EDPT) at a rate too fast for other reactions to take place. Why this process occurs so efficiently is typ...

Photoacids like substituted naphthalenes (X = OH, NH3+, COOH) are aromatic in the S0 state and antiaromatic in the S1 state. Nucleus independent chemical shifts analyses reveal that deprotonation relieves antiaromaticity in the excited conjugate base, and that the degree of “antiaromaticity relief” explains why some photoacids are stronger than oth...

Hydrogen bonding principles are at the core of supramolecular design. This overview features a discussion relating molecular structure to hydrogen bond strengths, highlighting the following electronic effects on hydrogen bonding: electronegativity, steric effects, electrostatic effects, π‐conjugation, and network cooperativity. Historical developme...

he mechanistic details of the aldol addition of N‐amino cyclic carbamate (ACC) hydrazones is provided herein from both an experimental and computational perspective. When the transformation is carried out at room temperature the anti‐aldol product is formed exclusively. Under these conditions the anti‐ and syn‐aldolate intermediates are in equilibr...

In this work we describe the synthesis of sterically encumbered 1,5-diaryl-3-cyanoformazanate bis-cyclometalated iridium(III) complexes, two of which undergo redox-neutral cyclization during the reaction to produce carbon-bound 2-aryl-4-arylazo-2H-1,2,3-triazolide ligands. This transformation offers a method for accessing 2-aryl-4-arylazo-2H-1,2,3-...

Before the development of an ozone layer in the Archean atmosphere, the flux of UV radiation reaching Earth was suggested to be several orders of magnitude higher than it is today. For the emerging biomolecules, constant exposure to strong UV irradiation meant that useful molecules had to be resistant to UV damage and harmful photochemical reaction...

Significance Excited-state proton transfer (ESPT) is universally recognized as a reaction that relaxes the energy of a photoexcited organic compound. It is commonly found in many light-driven processes. Here we identify decisive principles underlying why and when ESPT happens. Our computational investigation of prototypical ESPT reactions finds tha...

Imidazole and benz-imidazole based different NHC ligands have been designed to make Cu(I)@NHC complex. Calculated vertical electron affinity suggests that all the ligands are belongs to a special type of molecule, superalkali and have very good non linear activity. All of them form Cu(I)@NHC complexes which have a trinuclear Cu3 core. The nucleus i...

Creating stimuli-responsive materials with switchable solid-state luminescence remains a challenge. We report that the solvation of a noval organic fluorophore can be ulitized to prepare such a material, which emits...

Cyclometalated iridium complexes have emerged as top-performing emitters in organic light-emitting diodes (OLEDs) and other optoelectronic devices. A persistent challenge has been the development of cyclometalated iridium complexes with deep blue luminescence that have the requisite color purity, efficiency, and stability to function in color displ...

Baird's rule explains why and when excited-state proton transfer (ESPT) reactions happen in organic compounds. Bifunctional compounds that are [4n+2] π-aromatic in the ground state, become [4n+2] π-antiaromatic in the first 1 ππ* states, and proton transfer (either inter-or intra-molecularly) helps relieve excited-state antiaromaticity. Computed nu...

p>Baird’s rule explains why and when excited-state proton transfer (ESPT) reactions happen in organic compounds. Bifunctional compounds that are [4 n +2] π-aromatic in the ground state, become [4 n +2] π-antiaromatic in the first ¹ππ* states, and proton transfer (either inter- or intra- molecularly) helps relieve excited-state antiaromat...

Dicarboxylic acids are important chemicals in human metabolism and various industries. Differentiating among their isomers and members of homologous series is a challenge, due to their similar properties. We show...

Density functional theory computations and block-localized wavefunction analyses for 57 hydrogen-bonded base pairs document excellent linear correlation between the gas-phase association energies and the degree of aromaticity gain of paired bases (r = 0.949), challenging prevailing views of factors that underlie the proposed electronic complementar...

Redox-active platinum(II) azo-iminate complexes are prepared from formazan precursors via proton-coupled reduction accompanied by N−N bond cleavage. Four examples of this reaction are shown, and the compounds thus prepared are all characterized by X-ray crystallography, cyclic voltammetry, and UV−vis absorption spectroscopy. Ligand-centered redox e...

A chiral auxiliary-based diastereoselective transformation that entirely avoids the stereochemically mismatched pairing, providing equally high levels of asymmetric induction in the formation of each diastereomer is described. In particular, we show that chiral nonracemic methyl ketones undergo α,α-bisalkylation using phenylalanine-derived N-amino...

Correction for ‘Aromaticity gain increases the inherent association strengths of multipoint hydrogen-bonded arrays’ by Chia-Hua Wu et al. , Chem. Commun. , 2018, 54 , 3512–3515.

The bidentate aromatic adsorbate, (4,6-bis(octadecyloxy)-1,3-phenylene)-dimethanethiol (R1ArmDT), with the specific design of extended S-S distance and a geometric constraint to resist cyclic disulfide formation was synthesized. The film formation and thermal stability of self-assembled monolayers (SAMs) derived from R1ArmDT were investigated and c...

Textbook explanations for the associations of multipoint hydrogen-bonded arrays have long hinged on the secondary electrostatic interaction (SEI) model, which suggests that array association strengths depend on the proton donor (D) and acceptor (A) patterns of the interacting units. Here, computational results based on the block-localized wavefunct...

Surprisingly large “resonance-assistance” effects may explain how some enzymes form extremely short, strong hydrogen bonds to stabilize reactive oxyanion intermediates and facilitate catalysis. Computational models for several enzymic residue-substrate interactions reveal that when a π-conjugated, proton donor (XH) forms a hydrogen bond to a charge...

From DNA base pairs to drug-receptor binding, hydrogen (H-)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored; H-bond strength modulation due to enhancement or disruption of heterocycles' aromaticity is revealed by comparing homodimer H-bond energies of aromatic heterocycles with...

From DNA base pairs to drug-receptor binding, hydrogen (H-)bonding and aromaticity are common features of heterocycles. Herein, the interplay of these bonding aspects is explored; H-bond strength modulation due to enhancement or disruption of heterocycles' aromaticity is revealed by comparing homodimer H-bond energies of aromatic heterocycles with...

This in silico survey shows that changes in the (anti)aromatic character of π-conjugated heterocycles can be used to fine-tune their hydrogen (H-) bond strengths. Upon H-bonding dimerization, the π-electrons of these rings can be polarized to reinforce or disrupt their (anti)aromatic π-conjugated circuits (πCCs), and stabilize or destabilize the re...

Formazanates are a ligand class featuring a 1,2,4,5-tetraazapentadienyl core, with variable substitution at the 1, 3, and 5 positions. Here we describe a set of four heteroleptic cylcometalated platinum complexes containing triarylformazanate ligands. The complexes are prepared by metathesis reactions of chloro-bridged dimers [Pt(C∧N)(μ-Cl)]2 (C∧N...

The phenol-phenolate anionic complex was studied in vacuo by negative ion photoelectron spectroscopy using 193 nm photons and by density functional theory (DFT) computations at the ωB97XD/6-311+G(2d,p) level. We characterize the phenol-phenolate anionic complex as a proton-coupled phenolate pair, i.e., as a low-barrier hydrogen bond system. Since t...

Natural bond orbital (NBO) analyses and dissected nucleus-independent chemical shifts (NICSπ z z ) were computed to evaluate the bonding (bond type, electron occupation, hybridization) and aromatic character of the three lowest-lying Si2CH2 (1-Si, 2-Si, 3-Si) and Ge2CH2 (1-Ge, 2-Ge, 3-Ge) isomers. While their carbon C3H2 analogs favor classical alk...

The aromatic character of fused polycyclic systems varies with the nature of their annulated rings. Computed extra cyclic resonance energies (ECREs) reveal that the central six membered rings (6MRs) of the heterocyclic fused congeners 1-5 are "[6]radialene-like", but that the central 6MRs of triphenylene 9, coronene 10, and isocoronene 11 are "benz...

Complexity of the potential energy surface of the 9-homocubyl cation is revealed by Born-Oppenheimer molecular dynamics simulations and high ab initio levels. The stereospecific automerizations observed experimentally involve bridged ions, which have either an aromatic or an anti-aromatic character. New pathways leading to more stable isomers are u...

The conventional view that the σCC and σCH bonds in alkanes and unsaturated hydrocarbons are so highly localized that their non-steric interactions are negligible is scrutinized by the block-localized wavefunction (BLW) method. Even molecules considered conventionally to be “strain free” and “unperturbed” have surprisingly large and quite significa...

Aromaticity is an essential concept in chemistry, employed to account for the unusual stability, reactivity, molecular structures, and other properties of many unsaturated organic compounds. This concept was later extended to inorganic molecules and to saturated systems with mobile electrons, as well as to transition structures, the focus of the pr...

Aromaticity, a highly stabilizing feature of molecules with delocalized electrons in closed circuits, is generally restricted to 'Hückel' systems with 4n+2 mobile electrons. Although the Möbius concept extends the principle of aromaticity to 4n mobile electron species, the rare known examples have complex, twisted topologies whose extension is unli...

Heilbronner's Hückel molecular orbital treatment of Möbius 4n-π annulenes is revisited. When uneven twisting in π-systems of small Möbius rings is accounted for, their resonance energies become comparable to iso-π-electronic linear alkenes with the same number of carbon atoms. Larger Möbius rings distribute π-twisting more evenly but exhibit only m...

Computed aromatic stabilization energies (ASEs) and dissected nucleus independent chemical shifts (NICSπzz) quantify the effect of hyperconjugation on the (anti)aromaticities of the planar conformations of three, five, seven, and nine membered (CnHn)CR2 (R = H, SiH3, F) rings. CH2 and especially C(SiH3)2 groups supply two "pseudo" π electrons hyper...

Computational investigations of the thermochemical stability and kinetic persistence of binary S(x)N(y) compounds, SN(2), S(2)N(2), S(3)N(2), S(4)N(2), SN(4), S(2)N(4), S(3)N(4), and S(4)N(4), explain why some S(x)N(y) stoichiometries exist but not others. There is no direct link between the Hückel 4n + 2 π-electron count rule and the computed heat...

Like the larger non-planar Möbius rings, porphyrinoid aromaticity is not due primarily to the macrocyclic π conjugation of the corresponding annulene perimeters. The block-localized wavefunction (BLW) derived aromatic stabilization energies (ASE) of several porphyrinoids reveal that, on a per atom basis, the appended 6π electron heterocycles of por...

Notwithstanding their two (i.e., 4n + 2) π electrons, four-membered ring systems, 1-4, favor puckered geometries (1a-4a) despite the reduction in vicinal π overlap and in the ring atom bond angles. This nonplanar preference is due to σ → π* hyperconjugative interactions across the ring (A) rather than to partial 1,3-bonding (B). Electronegative sub...

Reduction of a 4,5,6-triphospha[3]radialene gave the corresponding isolable dianionic species. Despite having two deltate dianion-like π-electrons delocalized over the central framework, its small NICS(0)(πzz) value (only -2.2 ppm) indicates only limited aromaticity.

Protonated pyrrole cations are produced in a pulsed discharge/supersonic expansion source, mass-selected in a time-of-flight spectrometer, and studied with infrared photodissociation spectroscopy. Vibrational spectra in both the fingerprint and C-H/N-H stretching regions are obtained using the method of tagging with argon. Sharp vibrational structu...

C(60) does not have "superaromatic" or even aromatic character, but is a spherically π antiaromatic and enormously strained species. This explains its very large and positive heat of formation (610 ± 30 kcal mol(-1)). The π electron character of C(60) was analyzed by dissected nucleus independent chemical shifts (NICS). The results were employed to...

The first example of a dyotropic rearrangement of an enantiomerically pure, conformationally unconstrained, vicinal dibromide confirms theoretical predictions: D and L-1,2-dibromo-1,2-diphenylethane racemise stereospecifically in refluxing benzene without crossover to the meso-isomer. An orbital analysis of this six-electron pericyclic process is p...

The high energy of cyclobutadiene (CBD) is not due primarily to "anti-aromaticity," but rather to angle strain, torsional strain, and Pauli repulsion between the parallel CC bonds. Estimations including block-localized wavefunction (BLW) computations conclude that the enormous ring strain (ca. 60 kcal mol(-1)) far exceeds its antiaromatic destabili...

The transition states (TSs) of 5-endo-dig and 5-endo-trig anionic ring closures are the first unambiguous examples of nonpericyclic reactions with TSs stabilized by aromaticity. Their five-center, six-electron in-plane aromaticity is revealed by the diatropic dissected nucleus-independent chemical shifts, -24.1 and -13.7 ppm, respectively, resultin...

Two trannulene moieties fused to each other by means of perfectly planar cycloalkane rings comprise an interesting class of molecules (above) named "imperilenes". Based on computed geometries and NICS(zz) values, only the [5], [7], and [9]imperilene singlet states as well as the 4+ charged [4], [6], and [8]imperilenes and their higher energy neutra...

The nature of the bonding and the aromaticity of the heavy Group 14 homologues of cyclopropenylium cations E3H3+ and E2H2E'H+ (E, E' = C-Pb) have been investigated systematically at the BP86/TZ2P DFT level by using several methods. Aromatic stabilization energies (ASE) were evaluated from the values obtained from energy decomposition analysis (EDA)...

Quantitative evaluations of the aromaticity (antiaromaticity) of neutral exocyclic substituted cyclopropenes (HC)(2)C=X (X = BH to InH (group 13), CH(2) to SnH(2) (group 14), NH to SbH (group 15), O to Te (group 16)) by their computed extra cyclic resonance energies (ECRE, via the block-localized wave function method) and by their aromatic stabiliz...

The most refined nucleus-independent chemical shift index (NICS(0)(πzz)) and the extra cyclic resonance energies (ECREs), based on the block localized wave function (BLW) method, show that the aromaticity of all azines is like that of benzene. The same is true for aza-naphthalenes relative to naphthalene. The lower relative energies of isomers with...

Although surprising, the nonplanarity of C(2h) C(4)F(4) is not unique. While C(6)F(6) is planar, other members of the (CF)(n) family, for example, C(5)F(5)(-), C(6)F(6)(-), C(7)F(7)(-), and triplet C(7)F(7)(-) are not. C(2h) C(4)F(4) is not aromatic, as claimed (see above), but its antiaromaticity is reduced relative to the planar D(2h) form due to...

The representative isodesmic reactions shown in the Abstract graphic for (CH)(4)X(6) hexaheteroadamantane derivatives reveal energetic nonadditivity to remarkably different extents: while the electropositive element stabilizations are exceptionally large and the pnictide and hexaoxaadamantane stabilizations are more modest, the sulfur and selenium...

(figure represented) Probe it: The new BLW-ICLO approach evaluates the magnetic responses of molecules in which conjugative interactions are "disabled" (see picture, red bonds). The NMR spectroscopy parameters of the localized structures provide ideal non-aromatic olefinic hydrogen δ(1H) references for the fully conjugated systems.

The reactivity and regioselectivity of the electrophilic chlorination, nitration, and alkylation of benzene derivatives were rationalized by comparing literature data for the partial rate factors (ln f) for these S(E)Ar processes with theoretical reactivity parameters. The Electrophile Affinity (Ealpha), a new quantity, is introduced to characteriz...

Despite having six highly electronegative F's, perfluorobenzene C(6)F(6) is as aromatic as benzene. Ab initio block-localized wave function (BLW) computations reveal that both C(6)F(6) and benzene have essentially the same extra cyclic resonance energies (ECREs). Localized molecular orbital (LMO)-nucleus-independent chemical shifts (NICS) grids dem...

A theoretical study of the geometries, energies, dissociation pathways, and aromaticity of the isomeric sulfur-nitrogen S(2)N(3)(+) rings reveals that the experimentally known 1,2-isomer is only stable kinetically. A rather high barrier inhibits its dissociation into the slightly lower energy N(2) and NSS(+) fragments via a stepwise mechanism. A se...

Dewar proposed the sigma-aromaticity concept to explain the seemingly anomalous energetic and magnetic behavior of cyclopropane in 1979. While a detailed, but indirect energetic evaluation in 1986 raised doubts-"There is no need to involve 'sigma-aromaticity',"-other analyses, also indirect, resulted in wide-ranging estimates of the sigma-aromatic...

Despite having 4n pi electrons, dihydrodiazapentacenes are more viable than their 4n+2 pi azapentacene counterparts. Ab inito valence bond block-localized wave function (BLW) computations reveal that despite having 4n pi electrons, dihydrodiazapentacenes are stabilized and benefit substantially from four dihydropyrazine ethenamine (enamine) conjuga...

The aromatic stabilization energy (ASE) of pyrene, evaluated with both isodesmic equation and ab initio valence bond (VB) theory-based block localized wavefunction (BLW) methods, gives consistent results (ca 74 kcal/mol). Biphenyl, phenanthrene and benzene, evaluated similarly, all have essentially the same ASEs per ring carbon. The aromaticity of...

Cycloheptatriene (Cs) is firmly established to be a neutral homoaromatic molecule based on detailed analyses of geometric, energetic, and magnetic criteria. Substituents at the 7 (methylene) position, ranging from the electropositive BH2 to the electronegative F, favor the equatorial conformation but influence the aromaticity only to a small extent...

The geometries of a series of [n](2,7)pyrenophanes (n = 6−12) were optimized at the B3LYP/6-311G** DFT level. The X-ray crystal structures determined for the [9](2,7)- and [10](2,7)pyrenophanes agreed excellently with the computed structures. The degree of nonplanarity of the pyrene moiety depends on the number of CH2 groups in the aliphatic bridge...

The synthesis and X-ray characterization of two new dialkynylated diazatetracenes and the corresponding N, N-dihydrodiazatetracenes are reported. The dialkynylated heteroacenes are packed in a brick-wall motif that enforces significant overlap of their pi-faces. Cyclic voltammetry indicates that the dehydrogenated forms are easily reduced to their...

An antiaromatic-aromatic pair of peralkynylated heterocycles readily interconvert via redox reactions. [reaction: see text]