One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• ] for the state-specific solvation of the vertical excitation was included. The computations reveal that the longest wavelength absorption maximum appears at 541 nm, i.e., at a comparable energy as in the experimental spectrum. This transition is exclusively dominated by the HOMO–LUMO transition. The

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• ) level by using the energies of the corresponding radical cation and anion. Thus, the first electronic transition is predicted at 401 nm (f = 0.30). It is essentially the HOMO → LUMO transition. The next five electronic transitions between 333 and 300 nm are weak (f = 0.001–0.003) and involve mostly the

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• [10]. Alkyl chains or other functional groups can donate or withdraw electron density from the polymer chain, for example by inductive effects, altering the HOMO–LUMO levels and subsequent band gap in the process. One type of substituent that can be used is a perfluoroalkyl chain, where the high

• that the excited state of T1-3FTh undergoes a greater conformational change before emission than that of T1-4FTh, which is further evidence of the greater planarity in the T1-4FTh ground state compared to that of its isomer. The optical HOMO–LUMO gaps were estimated from the onset of absorption and

• were recorded as 3.20, 3.12 and 3.03 eV for T1-3FTh, T1-4FTh and T4-4FTh, respectively. The HOMO–LUMO gap for T1-3FTh and T1-4FTh is slightly narrower than that for T1; however, there is not much difference between the HOMO–LUMO gap of T4-4FTh and that of T4. The results for the cyclic voltammetry of

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

• Sofia Telitel,
• Frédéric Dumur,
• Thomas Faury,
• Bernadette Graff,
• Mohamad-Ali Tehfe,
• Didier Gigmes,
• Jean-Pierre Fouassier and
• Jacques Lalevée

Beilstein J. Org. Chem. 2013, 9, 877–890, doi:10.3762/bjoc.9.101

• supporting a clear ππ* character of the HOMO–LUMO transition, as evidenced in Figure 2 for the investigated derivatives. For the various π-core/pyrene substituent combinations, different coupling strengths can be observed (Figure 2). Strong couplings of the MOs lead to red-shifted transitions compared to

• molecules, (B) in toluene. HOMO–LUMO orbitals for Py_2, Py_3, Py_5, Py_6, Py_8, Py_11 and Py_12 involved in the π–π* transition (calculated at UB3LYP/6-31G* level; for Py_5 and Py_11, the alkyl chains have been simplified to reduce the computational cost). Fluorescence quenching of 1Py_3 by the

Superstructures of fluorescent cyclodextrin via click-reaction

• Arkadius Maciollek,
• Helmut Ritter and
• Rainer Beckert

Beilstein J. Org. Chem. 2013, 9, 827–831, doi:10.3762/bjoc.9.94

• exclusion of the fluorophore moiety from the hydrophobic cavity of CD. This exchange causes a change in the HOMO–LUMO gap [14][15]. Figure 3 shows the fluorescence spectra of 3 in aqueous solution. Upon addition of potassium adamantane-1-carboxylate the maximum wavelength changes from 417 to 442 nm and the

The β-cyclodextrin/benzene complex and its hydrogen bonds – a theoretical study using molecular dynamics, quantum mechanics and COSMO-RS

• Jutta Erika Helga Köhler and
• Nicole Grczelschak-Mick

Beilstein J. Org. Chem. 2013, 9, 118–134, doi:10.3762/bjoc.9.15

• when it was positioned vertically. The AM1 HOMO/LUMO gap of the empty β-CD with about 12 eV is lowered to about 10 eV in the complex, in agreement with data from the literature. AM1 IR spectra displayed a splitting of the O–H frequencies of cyclodextrin upon complex formation. At the BP/TZVP-DISP3

• moment, HOMO/LUMO molecular orbitals and IR spectral data, were analysed with GaussView. Step 2: The four AM1 optimised β-CD models were used as starting structures in our QM calculations by using Turbomole v. 6.4 with COSMO-RS [31]. Two models were calculated for each structure, i.e., the structure in

• . Benzene was slightly distorted in each cavity, as can be seen from its energy and dipole moment inside the complex. Inside the β-CD/benzene complex the benzene neither in a parallel position nor in vertical position adopted an exact central position as displayed in Figure 2. Our calculated AM1 HOMO/LUMO

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• phosphanes the pyramidalization angle d(RNRR/RPRR) (Figure 10), the HOMO–LUMO gap (ΔHOMO–LUMO), and the s/p composition of the lone pair from NBO analysis has been compiled in Table 11 for selected systems. From the data above it can easily be seen that the RXRR angle in phosphanes is systematically smaller

• . The HOMO–LUMO gap, in contrast, shows no significant correlation with the degree of pyramidalization but depends largely on the substitution pattern. Mosher’s cation affinities (MOSCA) For the multitude of stereoselective organocatalytic transformations the affinity of chiral Lewis bases towards

Toward unidirectional switches: 2-(2-Hydroxyphenyl)pyridine and 2-(2-methoxyphenyl)pyridine derivatives as pH-triggered pivots

• Christina Tepper and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2012, 8, 977–985, doi:10.3762/bjoc.8.110

• small coefficient at the protonated nitrogen atom, the energetic lowering of the HOMO (Δε = −3.89 eV) caused by the protonation is less pronounced than the one observed for the LUMO (Δε = −5.32 eV). The resulting decrease of the HOMO–LUMO gap is responsible for the bathochromic shift of the

Thiophene-based donor–acceptor co-oligomers by copper-catalyzed 1,3-dipolar cycloaddition

• Stefanie Potratz,
• Amaresh Mishra and
• Peter Bäuerle

Beilstein J. Org. Chem. 2012, 8, 683–692, doi:10.3762/bjoc.8.76

• unit could be observed. From the optoelectronic data we deduced a HOMO–LUMO energy level diagram including band gaps for the novel donor–acceptor materials 5, 6 and 10–14 (Figure 2). HOMO values were taken from the onset of oxidation and the internal reference Fc/Fc+ was set to −5.1 eV versus vacuum

• , 121.89, 125.26, 126.59, 128.56, 132.63, 136.68, 143.41; CIMS m/z: (M + H) 377, (M − N2) 349, (M − N4) 320; HRMS–ESI (m/z): (M + Na) calcd for C18H12N6NaS2, 399.0457; found, 399.0452. UV–vis spectra of 5, 10 and 11 (a) and 12–14 (b) in dichloromethane ([c] = 5 × 10−5 M) at room temperature. HOMO–LUMO

Synthesis, solid-state fluorescence properties, and computational analysis of novel 2-aminobenzo[4,5]thieno[3,2-d]pyrimidine 5,5-dioxides

• Kenichirou Yokota,
• Masayori Hagimori,
• Naoko Mizuyama,
• Yasuhisa Nishimura,
• Hiroshi Fujito,
• Yasuhiro Shigemitsu and
• Yoshinori Tominaga

Beilstein J. Org. Chem. 2012, 8, 266–274, doi:10.3762/bjoc.8.28

• reproduced by a series of ab initio quantum-chemical calculations. Keywords: amino group; fluorescence; HOMO/LUMO; pyrimidine; solid-state; Introduction Solid-state fluorescent compounds are currently attracting considerable interest from both theoretical and practical standpoints [1][2][3][4]. Recently

• structures, the HOMO and LUMO of 3a are depicted in Figure 1. The λmax was assigned as the HOMO–LUMO π–π* excitation (configuration weight = 0.697) with an oscillator strength of 0.096 at 335 nm. The next theoretical peak appeared at 290 nm, derived from (HOMO − 1) to LUMO excitations, considerably separated

• carried out ab initio molecular-orbital calculations, focused on 3a (Figure 3). The computed key bond lengths are shown in Table 3. Comparison of the S0 (DFT) and S1 (CIS) bond lengths shows that the S0→S1 (dominant HOMO→LUMO) transition is reflected in the bond-length variations. The C4–C5 bond, with a

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• chromophore π-conjugated backbone. In contrast to 88–93, the presence of two (or four) N,N-dimethylamino donors and the systematic extension of the π-linkers in 95–100 resulted in a bathochromically shifted CT-band, lowered electrochemically measured and calculated HOMO–LUMO gaps, and enhanced first-order

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• with the increase in π-electron delocalisation due to the addition of the conjugated phenyl ring. This increase in conjugation is also evidenced by a slight reduction in the optically determined HOMO–LUMO gap of 1a and 1b (2.2 eV for both, Table 2). The solid-state absorption spectra of 1a and 1b are

• very similar, but the optical HOMO–LUMO gaps in the solid state are red-shifted compared to those in solution (2.0 eV). UV–vis spectroelectrochemical measurements (SEC) were performed in acetonitrile on functionalised sexithiophene 1b and nonfunctionalised sexithiophene 2b as thin films drop-cast onto

• separation potentials of 1b in the solid state compared to 2b. The HOMO–LUMO gap was determined from the difference in the onsets for the reduction and first-oxidation processes. Comparison of the optical properties of 1a, 1b, 2a and 2b in solution and solid state. The HOMO–LUMO gap was determined from the

Predicting the UV–vis spectra of oxazine dyes

• Scott Fleming,
• Andrew Mills and
• Tell Tuttle

Beilstein J. Org. Chem. 2011, 7, 432–441, doi:10.3762/bjoc.7.56

• 0.4–0.6, while the major contribution (HOMO–LUMO) remains constant across the series, resulting in the slight variation in the Λ values observed for this dye. Figure 5 illustrates that the orbital overlap for the solvent phase calculations is largely unaffected by the choice of functional. This is due

• primarily to the fact that the predominant contribution to the excitation energy and the nature and overlap of the orbital pair (HOMO–LUMO) is conserved across the different methods. In the gas-phase TD-DFT calculations the number of orbital pairs contributing towards the λmax excitation varies with respect

• to the solvent calculations – two orbital pairs contribute in the gas-phase calculations for 2, 3, 5, 7, 9, and 10 – however, a comparable Λ value is obtained in most cases due to the dominance of the HOMO–LUMO contribution in these excitations as well. The strong overlap between the occupied and

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• thiophene-based (well-established) materials, compounds with additional electron-poor moieties are in focus, as they are known to shift the HOMO and LUMO levels towards lower energies, thus increasing the compounds' stability against oxidation. In addition, the HOMO-LUMO gap is reduced (by the donor

• ). It has to be kept in mind that the calculated values correspond to vertical excitation energies between electronic states while the measured optical spectra include vibronic effects. The dominating signals in the spectra of quaterthiophene 19 and sexithiophene 20 correspond to the HOMO-LUMO

• larger delocalized π-system, which lowers the HOMO-LUMO gap as discussed above. The difference density of 12a (Figure 2c) shows that the S0-S1 excitation leads to an intramolecular charge transfer (CT) from the thiophenes to the phenazine part of the molecule. These calculations verify our initial

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• . These results indicate that the fluorescence emission arises from excited state intramolecular charge transfer in these molecules where the triphenylene chromophore acts either as a donor or as an acceptor depending upon the nature of the substituent on the phenyl ring. HOMO–LUMO energy gaps have been

• substituted with electron withdrawing groups on the phenyl ring. HOMO–LUMO energy gaps have been estimated based on electrochemical studies and compared with those obtained from absorption spectroscopy. Results and Discussion Synthesis 2-Ethynyltriphenylene (4) was synthesized by coupling 2-iodotriphenylene

• potentials, as well as to estimate the HOMO–LUMO gap of these derivatives [31][32][33][34][35]. All the compounds showed a single irreversible oxidation peak and multiple reduction peaks. The HOMO–LUMO gap was estimated from the CV data as the difference between the oxidation peak potential and the reduction

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• the “normal” 5-substituted isoxazoline is formed. Hence, the nitrodecene 123 gives rise to only the nine-membered carbocycle 125 upon reaction with phenyl isocyanate. The matching HOMO-LUMO interactions for such cycloadditions favour the formation of 126 but ring strain and transannular steric effects

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• formation of the target molecule [19][20] or a separate preparation of the donor as well as the acceptor moieties and their final combination [21][22]. It is already well known that the HOMO/LUMO gap and polarizability of the push-pull systems with the given donors and acceptors can be finely tailored by

High stereoselectivity on low temperature Diels- Alder reactions

• Luiz Carlos da Silva Filho,
• Valdemar Lacerda Júnior,
• Mauricio Gomes Constantino,
• Gil Valdo José da Silva and
• Paulo Roberto Invernize

Beilstein J. Org. Chem. 2005, 1, No. 14, doi:10.1186/1860-5397-1-14

• less reactive, while β-methylated cycloenones (4 and 6) did not react at all. The rather perplexing low reactivity of β-methylated cycloenones was already observed by Wenkert et al. [17]. We are presently carrying out HOMO-LUMO and transition state calculations, seeking for the reasons that could

• product. This would increase the usual difference between the two transition states, normally due mainly to π orbital overlaps. As already mentioned, we are performing HOMO-LUMO and transition states calculations to verify some structural factors influences on the course of these reactions. Conclusion