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OBJECTIVE Monitoring the intraoperative motor evoked potentials (MEPs) in pediatric craniotomy is challenging because of its low detection rate, which makes it unreliable. Tetanic stimulation of the peripheral nerves of the extremities and pudendal nerves prior to transcranial electrical stimulation (TES) or direct cortical stimulation (DCS) amplifies the MEPs. The authors investigated the effects of MEP amplification following tetanic stimulation of the median and tibial nerve or the pudendal nerve in pediatric patients undergoing craniotomy. METHODS This prospective observational study included 15 patients ≤ 15 years of age (mean age 8.9 ± 4.9 years) undergoing craniotomy. MEPs were obtained with TES (15 cases) or DCS (8 cases)—conventional MEP without tetanic stimulation (c-MEP) and MEP following tetanic stimulation of the unilateral median and tibial nerves (mt-MEP) or following tetanic stimulation of the pudendal nerve (p-MEP) were used. Compound muscle action potentials were elicited from the abductor pollicis brevis, gastrocnemius, tibialis anterior, and abductor hallucis longus muscles. The authors compared the identification rate and the rate of amplitude increase of each MEP. RESULTS For both TES and DCS, the identification and amplitude increase rates were significantly higher in cases without preoperative hemiparesis for p-MEPs than in those for c-MEPs and mt-MEPs. In comparison to patients with preoperative hemiparesis, p-MEPs displayed a higher identification rate, with fewer false negatives in DCS cases. CONCLUSIONS In pediatric craniotomy, the authors observed the amplification effect of MEPs with pudendal nerve tetanic stimulation and the amplification effect of DCS on MEPs without increasing false negatives. These findings suggested the likelihood of more reliable intraoperative MEP monitoring in pediatric cases.

The high design flexibility of organic semiconductors should lead to diverse and complex electronic functions. However, currently available high-performance organic semiconductors are limited in variety; most of p-type materials are based on thienoacenes or related one-dimensionally (1D) extended π-conjugated systems. In an effort to expand the diversity of organic semiconductors, we are working on the development of tetrabenzoporphyrin (BP) derivatives as active-layer components of organic electronic devices. BP is characterized by its large, rigid two-dimensionally (2D) extended π-framework with high light absorptivity and therefore is promising as a core building unit of organic semiconductors for optoelectronic applications. Herein, we demonstrate that BP derivatives can afford field-effect hole mobilities of4 cm

A 10,20-bis(triisopropylsilylethynyl)tetrabenzo-5,15-diazaporphine (TIPS-TBDAP) was synthesized by the metal-template aza-annulation reaction. TIPS-TBDAP showed intense far-red fluorescence at 723 nm with a fluorescence quantum yield of 31% in chloroform solution. X-ray diffraction analysis revealed that TIPS-TBDAP forms a one-dimensional slipped [Formula: see text]-stacking structure in the single crystal state. TIPS-TBDAP is soluble in common organic solvents owing to the bulky substituents and solution-processed field-effect transistors (FETs) could be fabricated. Dip-coating and single-crystal FETs showed the maximum hole mobilities of 1.5× 10[Formula: see text] and 0.16 cm2 V[Formula: see text] s[Formula: see text], respectively.

The acene series, an important class of linearly polycyclic aromatic hydrocarbons, are of interest owing to their unique physicochemical features. With an increase in the number of fused benzene rings, acenes display an evolution of electronic structure and properties. Thus, efforts have been devoted to the synthesis of longer acenes, with dodecacene being the longest acene (12 fused benzene rings) reported to date. However, the formation of polymeric acenes with numerous benzene rings, namely polyacene, has yet to be realized. Herein, we present a methodology for the synthesis of polyacene mediated by a metal–organic framework. Nanoconfined synthesis of precursor polymers in the channels of the metal–organic framework and the subsequent dehydro-aromatization reaction produced polyacene that was overwhelmingly longer than the previously reported acenes. The scalable synthesis of polyacene allowed us to unveil the stability and electronic properties of polyacene, paving the way for their widespread applications in optoelectronic and magnetic devices.

Acenes, which are hydrocarbons comprising linearly fused benzene rings, have attracted considerable attention owing to their electronic structures and utility as organic electronic materials. However, the ease with which oligoacenes undergo oxidation increases with the number of linearly fused benzene rings owing to the increased energy of the highest occupied molecular orbital. The synthesis of naked oligoacenes with seven or more benzene rings is difficult because their open-shell structure renders them unstable. The recent development of a precursor method has enabled the in situ synthesis of oligoacenes under specific conditions and the spectroscopic observation of oligoacene in single crystals, in film matrices and under cryogenic conditions. Scanning tunneling microscopy and non-contact atomic force microscopy under ultra-high vacuum conditions have also made significant advances in the study of oligoacenes and oligoazaacenes. This paper reviews the recent progress in the synthesis of oligoacenes using precursors, with a particular focus on the chemical structures, synthesis, and reactivity of the precursors. The electronic properties of oligoacenes are also discussed in relation to the number of fused benzene rings, including their energy levels and spin states. These results will contribute to the synthesis and development of carbon nanomaterials with applications in the field of organic electronics.

Purpose Postoperative urinary dysfunction following lumbosacral spine surgery is devastating. To assess urinary function, we invented a pediatric urinary catheter equipped with electrodes for the direct transurethral recording of myogenic potential from the external urethral sphincter (EUS). This paper presents two cases in which urinary function was monitored intraoperatively by recording of motor-evoked potential (MEP) from EUS during lumbosacral spine surgery in children. Methods Two children (aged 2 and 6 years) were included in this study. One patient had no preoperative neurological dysfunction, while the other had frequent urination and urinary incontinence. A pair of surface electrodes was attached to a silicone rubber urethral catheter (6 or 8 Fr; diameter, 2 or 2.6 mm). The MEP from the EUS were recorded to assess the function of the centrifugal tract from the motor cortex to the pudendal nerve. Results Baseline MEP waveforms from the EUS were successfully recorded with latency and amplitude of 39.5 ms and 66 µV in patient 1 and 39.0 ms and 113 µV in patient 2, respectively. A significant decrease in amplitude was not observed during surgery in the two cases. No new urinary dysfunction and complications associated with the urinary catheter-equipped electrodes developed postoperatively. Conclusion Using an electrode-equipped urinary catheter, monitoring of MEP from the EUS could be applicable during lumbosacral surgery in pediatric patients.

A novel buckybowl and its chiral hybrids featuring eight-membered rings and helicene units have been synthesized and characterized. The resulting hybrid and its complex with C60 show promising ambipolar transport characteristics.

The charge transport properties of a polycyclic aromatic compound containing λ3-phosphinine was evaluated, demonstrating the potential of low-coordinate phosphorus compounds as organic semiconductors.

5,15-Bis(triisopropylsilyl)ethynyltetrabenzoporphyrin (TIPS-H2BP) gave a one-dimensionally extended columnar packing motif. The single crystal field-effect transistor of TIPS-H2BP exhibited clearly better hole mobility (2.16 cm2 V−1 s−1) than its metal complexes (ca. 0.1 cm2 V−1 s−1), with efficient charge transport through π–π stacking along the tetrabenzoporphyrin units.

The acene series, an important class of linearly polycyclic aromatic hydrocarbons, are of significant interest owing to their unique physicochemical features. With an increase in the number of fused benzene rings, acenes display an evolution of electronic structure and properties. Thus, tremendous efforts have been devoted to the synthesis of longer acenes, reaching dodecacene being the longest acene (12-fused benzene rings) reported to date. However, the formation of polymeric acenes with numerous benzene rings, namely polyacene (PA), has yet to be realized. Herein, we present a methodology for the synthesis of PA, as a long-sought-after compound, mediated by a metal−organic framework (MOF). Nanoconfined synthesis of precursor polymers in MOF channels and the subsequent dehydro-aromatization reaction produced PA that was overwhelmingly longer than the previously reported acenes. The scalable synthesis of PA could allow us to unveil the stability and electronic properties of PA, paving the way for their widespread applications in both the scientific and industrial fields.

Purpose Postoperative urinary dysfunction following lumbosacral spine surgery is devastating. To assess urinary function, we invented a pediatric urinary catheter equipped with electrodes for the direct transurethral recording of myogenic potential from the external urethral sphincter (EUS). This is the first report regarding the direct recording of motor-evoked potential (MEP) from EUS during lumbosacral spine surgery in children. Methods Two children (aged 2 and 6 years) were included in this study. One patient had no preoperative neurological dysfunction, while the other had frequent urination and urinary incontinence. A pair of surface electrodes was attached to a silicone rubber urethral catheter (6 or 8 Fr; diameter, 2 or 2.6 mm). The MEP from the EUS were recorded to assess the function of the centrifugal tract from the motor cortex to the pudendal nerve. Results Baseline MEP waveforms from the EUS were successfully recorded with latency and amplitude of 39.5 ms and 66 µV in patient 1 and 39.0 ms and 113 µV in patient 2, respectively. A significant decrease in amplitude was not observed during surgery in the two cases. No new urinary dysfunction and complications associated with the urinary catheter-equipped electrodes developed postoperatively. Conclusion Using an electrode-equipped urinary catheter, monitoring of MEP from the EUS could be applicable during lumbosacral surgery in pediatric patients.

Given neuromuscular blockade (NMB) can affect the amplitude and detection success rate of motor-evoked potentials (MEP), sugammadex may be administered intraoperatively. We evaluated the factors affecting the degree of residual NMB (i.e., the train-of-four [TOF] ratio) and the relationship between TOF ratio and MEP detection success rate in Japanese patients undergoing spine surgery. This single-center retrospective observational study included adults who underwent spine surgery under propofol/remifentanil anesthesia, received rocuronium for intubation, and underwent myogenic MEP monitoring after transcranial stimulation. TOF ratios were assessed using electromyography. Sugammadex was administered after finishing the MEP setting and the TOF ratio was ≤0.7. To identify factors affecting the TOF ratio, TOF ratio and MEP detection success rate were simultaneously measured after finishing the MEP setting; to compare the time from intubation to the start of MEP monitoring after NMB recovery between sugammadex and spontaneous recovery groups, multivariable analyses were performed. Of 373 cases analyzed, sugammadex was administered to 221 (59.2%) cases. Age, blood pressure, hepatic impairment, and rocuronium dose were the main factors affecting the TOF ratio. Patients with higher TOF ratios (≥0.75) had higher MEP detection success rates. The time from intubation to the start of MEP monitoring after NMB recovery was significantly shorter in patients administered sugammadex versus patients without sugammadex (P .0001). The MEP detection success rate was higher in patients with a TOF ratio of ≥0.75. Sugammadex shortened the time from intubation to the start of MEP monitoring after NMB recovery.

We report improved synthesis of the bicyclo[2.2.2]octadiene(BCOD)-fused 5,15-diazaporphyrin and meso-substituted derivatives by metal-template aza-annulation reaction. The obtained compounds act as the soluble precursors of tetrabenzo-5,15-diazaporphyrin (TBDAP) by thermal conversion. The substituents at meso-positions make significant differences in the optical properties and morphology in the thin film upon thermal conversion.

Pristine π-extended aromatic compounds are attractive as organic functional materials including organic semiconductors, but are difficult to synthesize in pure form because of their low solubility in common organic solvents. The precursor approach is a very useful method to synthesize pure π-extended aromatic compounds that cannot be prepared via traditional organic synthesis in flasks. In this approach, pure precursors are first prepared; these precursors are then converted quantitatively to the target molecules via a retro-Diels–Alder reaction or Strating–Zwanenburg photodecarbonylation reaction. This approach has also been used for the on-surface synthesis of the large acenes, heptacene and nonacene, under ultra-high vacuum in order to investigate their electronic properties, and is useful for the control of the packing structure of organic semiconductors in solution–processed films. The charge carrier mobilities of organic photovoltaics and organic field effect transistors have been improved using the precursor approach in combination with substituent effects. This account focuses on the synthesis and morphological control of aromatic compounds using the precursor approach in our group in the last decade.

We demonstrate on-surface deprotection of methylenedioxy groups which yielded graphene nanoribbons (GNRs) with edges functionalized by hydroxy groups. While anthracene trimer precursors functionalized with hydroxy groups did not yield GNRs, it was found that hydroxy groups are first protected as methylenedioxy groups and then deprotected during the cyclo-dehydrogenation process to form GNRs with hydroxy groups. The X-ray photoemission spectroscopy and non-contact atomic force microscopy studies revealed that ∼20% of the methylenedioxy turned into hydroxy groups, while the others were hydrogen-terminated. The first-principles density functional theory (DFT) study on the cyclo-dehydrogenation process was performed to investigate the deprotection mechanism, which indicates that hydrogen atoms emerging during the cyclo-dehydrogenation process trigger the deprotection of methylenedioxy groups. The scanning tunneling spectroscopy study and DFT revealed a significant charge transfer from hydroxy to the Au substrate, causing an interface dipole and the HOMO being closer to the Fermi level when compared with hydrogen-terminated GNR/Au(111). This result demonstrates on-surface deprotection and indicates a possible new route to obtain GNRs with desired edge functionalization, which can be a critical component for high-performance devices.

Administration of rocuronium to facilitate intubation has traditionally been regarded as acceptable for intraoperative motor evoked potential (MEP) monitoring because of sufficiently rapid spontaneous neuromuscular blockade recovery. We hypothesized that residual neuromuscular blockade, in an amount that could hinder optimal neuromonitoring in patients undergoing intracranial aneurysm clipping, was still present at dural opening. We sought to identify how often this was occurring and to identify factors which may contribute to prolonged blockade. Records of 97 patients were retrospectively analyzed. Rocuronium was administered to facilitate intubation with no additional neuromuscular blockade given. Prolonged spontaneous recovery time to a train-of-four (TOF) ratio of 0.75 after rocuronium administration was defined as 120 min, which was approximately when dural opening and the setting of baseline MEPs were occurring. Logistic regression analysis was used to identify factors related to prolonged spontaneous recovery time. Prolonged spontaneous recovery time to a TOF ratio of 0.75 was observed in 44.3% of patients. Multivariable analysis showed that only the dosage of rocuronium based on ideal body weight had a positive correlation with prolonged spontaneous recovery time (P = 0.01). There was no significant association between dosage of rocuronium based on total body weight, age, sex, or body temperature and prolonged recovery time. This study demonstrates that the duration of relaxation for MEP monitoring purposes is well-beyond the routinely recognized clinical duration of rocuronium. Residual neuromuscular blockade could result in lower amplitude MEP signals and/or lead to higher required MEP stimulus intensities which can both compromise monitoring sensitivity.

The recent surge in the efficiency of organic photovoltaic devices (OPVs) largely hinges on the reduction of energy loss (Eloss) that leads to improvements in open-circuit voltage (VOC). However, there are still many unclarified factors regarding the relationship between the molecular structure and VOC, hampering the establishment of widely applicable, effective principles for the design of active-layer materials. In this contribution, we examine the origin of the large VOC shifts induced by minor structural differences in end-alkyl substituents on a series of anthracene-based p-type compounds. The examined p-type compounds are all highly crystalline, thereby enabling detailed investigation of the molecular packing with X-ray diffraction analysis. At the same time, they are strongly aggregating and hardly soluble; therefore, they are deposited with the aid of a photoprecursor approach which we have been employing for controlled deposition of insoluble acene-based organic semiconductors. The resultant OPVs afford the highest VOC of 0.966 V when the end-alkyl groups are 2-ethylbutyl, and the lowest of 0.419 V when n-butyl is used in replacement of 2-ethylbutyl. X-ray diffraction analyses and density-functional-theory calculations indicate a critical impact of the non-slipped herringbone arrangement on the observed large loss in VOC. This type of molecular arrangement is prohibited when branched alkyl chains are introduced at the ends of linear π-systems, which we consider an important factor contributing to the relatively high VOC obtained with the 2-ethylbutyl derivative. These results may serve as a basis of useful molecular-design rules to avoid unnecessary losses in VOC., The cause of a large shift in open-circuit voltage induced by a minor difference in end-alkyl groups of p-type small molecules is examined via X-ray diffraction and computation, revealing a critical impact of molecular packing.

Tetrabenzoporphyrin (BP) holds attractive characteristics for optoelectronic applications, such as the large π-conjugated framework and high photoabsorption capability. However, its use in organic solar cells (OSCs) has been limited because of the extremely low solubility that hampers direct solution processing and also the high frontier-orbital energies that lead to low open-circuit voltage (VOC). Herein, we examine BP derivatives equipped with multiple strongly electron-withdrawing groups for photovoltaic applications. The derivatives are generated in thin films through a thermal precursor approach, wherein the corresponding bicyclo[2.2.2]octadiene-fused porphyrin derivatives are solution-cast, and then annealed to carry out the in situ retro-Diels-Alder reaction. The frontier-orbital energies of the resulting derivatives are effectively stabilized as compared to pristine BP to such a degree that they afford high VOC of up to 0.94 V when used as a donor or can even work as a new class of nonfullerene acceptor in OSCs. Single-crystal X-ray diffraction analyses demonstrate that the conformation of the BP framework largely varies from being near planar to highly curved depending on its substituents. The morphology of polymer:BP-derivative bulk-heterojunction films prepared by the thermal precursor approach also varies between the BP derivatives. These results can greatly extend the scope of both molecular design and morphology control for utilization of the BP chromophore toward achieving viable organic optoelectronic devices.

Substituted acene derivatives are regarded as promising materials for organic electronic devices such as organic light-emitting diodes (OLEDs). In particular, anthracene derivatives are known to exhibit good fluorescence property, with the air stability and solubility in common organic solvents expected to give advantages for solution-processed device fabrication. In this study, a series of bistriisopropylsilyl(TIPS)ethynyl anthracene derivatives with azaacene-containing iptycene wings have been synthesized by using condensation reactions. Effects of size of azaacenes on optical properties and packing structures were investigated. UV/Vis absorption and fluorescence spectra indicate that the π-elongation of iptycene units has small effects on the overall π-system, which is also supported by electrochemical measurements. Secondly, single-crystal X-ray analysis implies that the molecules likely have interactions with the iptycene units of adjacent molecules, while the iptycene wings and TIPSethynyl groups can prevent the central anthracene unit from undesirable non-radiative energy loss. Finally, the most emissive derivative was used as a dopant for solution-processed OLEDs, showing obvious electroluminescence with a luminance of over 920 cd m-2 .

Study design A prospective, within-subject study was conducted. Objective We aimed to compare the influence of anesthetic fade under maximum stimulation conditions between constant-current and constant-voltage stimulation techniques. Summary of background data The monitoring of muscle-evoked potentials after electrical stimulation to the brain [Br(E)-MSEP)] is useful for assessing the integrity of spinal cord motor tracts during major spine surgery. Nonetheless, Br(E)-MSEP responses are known to deteriorate over the duration of surgeries performed under general anesthesia. This phenomenon is known as anesthetic fade. Methods We recruited 117 patients undergoing various spinal surgeries from the cervical to the lumbar level. We excluded 29 cases with insufficient data. The decrease rate of the Br(E)-MSEP amplitude for each muscle was examined. Br(E)-MSEP monitoring with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions was applied. Compound muscle action potentials (CMAPs) were bilaterally recorded from the abductor pollicis brevis, deltoid, abductor hallucis, tibialis anterior, gastrocnemius, and quadriceps muscles. We defined the decrease rate as follows: (initial CMAPs-final CMAPs)/initial CMAPs × 100. Differences in the decrease rate were evaluated between stimulators, limbs (upper vs. lower), and operative time group (lowest quartile vs. highest quartile). Results The overall decrease rate (across all muscles) increased as the operative time increased, and the rate was higher in the lower limbs than in the upper limbs. In addition, the overall decrease rate was lower with constant-voltage stimulation than with constant-current stimulation. Furthermore, the decrease rate for constant-current stimulation was significantly higher than that for constant-voltage stimulation, regardless of the operative time. Conclusion The CMAP waveform with constant-voltage stimulation is less susceptible to anesthetic fade than that with constant-current stimulation, even during long surgeries. Level of evidence 3.

We demonstrate the effect of edge functionalization on the on-surface Ullmann coupling of nano-carbon materials. Unlike 10,10'-Dibromo-9,9'-bianthryl (DBBA), which is widely known to form anthracene polymers and armchair-edge graphene nanoribbons on Au(111), newly-developed precursor named 5-bromo-11(10-bromoanthracene-9-yl)anthra[2,3-b : 7,6-b']dithiophene (BABAT) with isomers, which has similar structure as DBBA with one anthracene substituted with anthradithiophene, was found to make intramolecular C-C bonding instead of long anthracene polymers after annealing at 200 °C on Au(111). The mechanism was investigated using first-principle density functional theory, which revealed that on-surface polymerization is not kinetically preferred in case of BABAT. The reaction rate of intramolecular C-C bonding of BABAT is ∼206 times faster than that of DBBA. The intramolecular C-C bonding in DBBA biradicals, on the other hand, do not take place because of faster reverse reaction. By referring to electron density of BABAT biradicals, it was concluded that thiophene functionalization modifies distribution of electron density in BABAT radicals and facilitates electrophilic addition, leading to intramolecular C-C bonding after 200 °C annealing. These results indicate that the design of radical moiety is particularly important in the on-surface Ullmann-type coupling.

Acenes are polycyclic aromatic hydrocarbons made up of linearly fused benzene rings. They are the smallest units of graphene and graphene nanoribbons, and have been extensively studied as organic semiconductor materials. Higher acenes are expected to have smaller band gaps required for practical use as organic electronic materials, but those with more than six benzene rings are poorly soluble in common organic solvents and unstable in aerobic condition to be synthesized and purified with traditional organic synthesis method. To overcome the obstacles, a precursor approach is a useful technique, where the soluble and stable precursors are purified enough and then converted to less-soluble and unstable target acenes in-situ.[1,2] Recently surface-assisted synthesis of higher acenes using precursors have attracted much attentions. Under ultra-high vacuum atmosphere, unstable acenes can be prepared from precursors by annealing, photoirradiation, or scanning tunneling microscopy (STM)-tip treatment on metal surface. We were successful to synthesize bis-diketone precursors of heptacene and nonacene. [3-6] The precursors were vacuum-deposited on Au(111) surface and converted to heptacene and nonacene by photoirradiation. Through combined STM, non-contact atomic force microscopy(nc-AFM) and scanning tunneling spectroscopy (STS) measurements, together with state-of-the-art first principles calculations, insight into the chemical and electronic structure of these elusive compounds was successful. It was revealed that nonacene has open-shell biradical structure in the ground state on Au(111). We were also successful to prepare tetraazaundecacene on Au(111) surface from bicyclo[2.2.2]octadiene (BCOD) precursor. [7] The tip-induced release of the protecting group can be employed to produce the targeted tetraazaundecacene species. The experimental frontier orbital gap, derived from the difference between PIR and NIR, is 1.35 eV. In this talk, the attraction and possibility of the “precursor approach” for the synthesis and application of acene compounds will be overviewed. References M. Suzuki, T. Aotake, Y. Yamaguchi, N. Noguchi, H. Nakano, K. Nakayama, H. Yamada, J. Photochem. Photobiol. C: Photochem. Rev. 2014, 18, 50-70. H. Yamada, D. Kuzuhara, M. Suzuki, H. Hayashi, N. Aratani, Bull. Chem. Soc. Jpn. 2020, 93, 1234-1267. J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. Di Giovannantonio, R. Widmer, M. Yamashita, N. Hieda, P. Ruffieux, H. Yamada, R. Fasel, Nat. Commun. 2019, 10, 861–864. J. I. Urgel, H. Hayashi, M. Di Giovannantonio, C. A. Pignedoli, S. Mishra, O. Deniz, M. Yamashita, T. Dienel, P. Ruffieux, H. Yamada, R. Fasel, J. Am. Chem. Soc. 2017, 139, 11658–11661. J. I. Urgel, M. Di Giovannantonio, G. Gandus, Q. Chen, X. Liu, H. Hayashi, P. Ruffieux, S. Decurtins, A. Narita, D. Passerone, H. Yamada, S.-X. Liu, K. Müllen, C. A. Pignedoli, R. Fasel, ChemPhysChem 2019, 20, 2360-2366. C. G. Ayani, M. Pisarra, J. I. Urgel, J. J. Navarro, C. Díaz, H. Hayashi, H. Yamada, F. Calleja, R. Miranda, R. Fasel, F. Martín, A. L. Vázquez de Parga, Nanoscale Horiz. 2021, 6, 744-750. K. Eimre, J. I. Urgel, H. Hayashi, M. D. Giovannantonio, P. Ruffieux, S. Sato, S. Ohtomo, Y. S. Chan, N. Aratani, D. Passerone, O. Gröning, H. Yamada, R. Fasel, C. A. Pignedoli, Nat. Commun. 2021. in press.

Azaacenes are the analogue of acenes, comprising nitrogen atoms in the carbon-based molecular skeleton, have been gaining attention because of their potential application in organic electronics and material science. However, it is normally difficult to synthesize such large aromatic molecules because of the poor solubility and low stability. On the other hand, we have developed precursor methods to overcome these problems. Briefly, bicyclo[2.2.2]octadiene(BCOD)-fused acenes can be converted its corresponding acenes by thermally induced retro-Diels–Alder reaction, while α-diketone-type precursors can be converted simply by photoirradiation.[1] Significantly, these precursor molecules are often more soluble and stable than its converted forms. More crucially, their corresponding acenes can be prepared quantitatively in solutions or in films, if the precursors are sufficiently pure. So far, by using the precursor methods, we have successfully synthesized polyacenes under anaerobic conditions either at ultrahigh vacuum conditions or at the interior of single crystals to avoid undesirable oxidation of the resulting polyacenes.[2–4] Here we report a series of tetraazapolyacene precursors synthesis. Briefly, the BCOD moieties were introduced in the tetraazaacenes as the thermally removable leaving group. The possibility of conversion of the precursors into its corresponding tetraazaacenes was examined by thermogravimetric analysis respectively. In addition, α-diketone-type precursor of tetraazaheptacene was also synthesized. Furthermore, we also report the one-pot synthesis of macrocyclic azacyclacene precursor by reacting bis-α-diketo-tetrahydro-diethanopentacene with benzene-1,2,4,5-tetraamine tetrahydrochloride. Here, the targeted compound was clearly confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The obtaining precursor compounds will be subjected to transformation to investigate its optical and physical properties. References H. Yamada, D. Kuzuhara, M. Suzuki, H. Hayashi, N. Aratani, Bull. Chem. Soc. Jpn. 2020, 93, 1234–1267. J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. D. Giovannantonio, R. Widmer, M. Yamashita, N. Hieda, P. Ruffieux, H. Yamada, F. Roman, Nat. Commun. 2019, 10, 861. H. Hayashi, N. Hieda, M. Yamauchi, Y. S. Chan, N. Aratani, S. Masuo, H. Yamada, Chem. Eur. J. 2020, 26, 15079–15083. K. Eimre, J. I. Urgel, H. Hayashi, M. D. Giovannantonio, P. Ruffieux, S. Sato, S. Otomo, Y. S. Chan, N. Aratani, D. Passerone, O. Gröning, H. Yamada, R. Fasel, C. A. Pignedoli, Nat. Commun. in press.

The on-surface photogeneration of nonacene from α-bisdiketone precursors deposited on nanostructured epitaxial graphene grown on Ru(0001) has been studied by means of low temperature scanning tunneling microscopy and spectroscopy. The presence of an unoccupied surface state, spatially localized in the regions where the precursors are adsorbed, and energetically accessible in the region of the electromagnetic spectrum where n–π* transitions take place, allows for a 100% conversion of the precursors into nonacenes. With the help of state-of-the-art theoretical calculations, we show that such a high yield is due to the effective population of the surface state by the incoming light and the ensuing electron transfer to the unoccupied states of the precursors through an inelastic scattering mechanism. Our findings are the experimental confirmation that surface states can play a prominent role in the surface photochemistry of complex molecular systems, in accordance with early theoretical predictions made on small molecules.

Optically active fullerenes, including C60 and C70 derivatives carrying organic substituents, are used in a range of applications because of their unique spectroscopic, catalytic, and chiral recognition properties. However, their inherent photoexcited chirality is yet to be elucidated because of their very poor fluorescence quantum yield (Φf). We synthesised a new chiral C70 derivative, X70A, with 20% yield, by reacting bis-borylated xanthene with C70 in a one-step double addition reaction, followed by a successful optical resolution. The isolation of two separate X70A enantiomers was confirmed by mirror-image circular dichroism spectroscopy in the range of 300–750 nm. In toluene, the enantiomeric pair of X70A clearly revealed mirror-image circularly polarised luminescence (CPL) spectra with a high |glum| value of 7.0 × 10−3 at 690 nm. The first fullerene-based deep-red CPL of X70A should provide a new guideline for the design of chiral nanocarbon materials.