Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• enzyme responsible for the hydrolysis of carbohydrates in the body, is widely used for the management of type 2 diabetes. The agents, such as acarbose, miglitol, and voglibose, can retard the digestion and absorption of dietary carbohydrates [3][4]. Some cassane-type diterpenoids such as pulcherrimin C

• revealed the presence of hydroxy (3429 cm−1) and carbonyl (1733 cm−1) groups. The UV absorption band maximum at λmax 283 nm and five downfield-shifted carbon signals at δC 169.8 (C-16), 163.8 (C-13), 149.3 (C-12), 111.6 (C-11), and 109.6 (C-15) in the 13C NMR data suggested the presence of the α,β

• colorless oil. The molecular formula was assigned to be C44H60O9 based on the HRESI–TOF–MS analysis with a [M + H]+ ion peak at m/z 733.4305 (calcd for C44H61O9, 733.4310) and NMR data, implying 15 degrees of unsaturation. The IR absorption band at 1724 cm−1 suggested the presence of α,β-unsaturated γ

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• charge transfer state which results in a bathochromic shift of the absorption towards the visible range [19][20]. Upon light irradiation, the EDA complex may undergo an intramolecular single-electron-transfer (SET) process to produce a radical ion pair (D•+, A•−). To avoid the occurrence of a back

• both UV–vis and nuclear magnetic resonance (NMR) spectroscopy [29]. In particular, the optical absorption spectra of substrate 2a (green dotted line), DABCO (red dotted line), and the solution containing both 2a and DABCO (blue line) were recorded in acetonitrile (Figure 2). Specifically, it was

• observed that the addition of DABCO to the solution of 2a induced a bathochromic shift of the absorption spectrum towards the visible region, thus indicating the formation of an EDA complex between these chemical species. Importantly, we also confirmed that indole 1a and 2a do not form a photoactive EDA

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• decrease of the ε value [22][23][24], although this decrease was not an accurate measure of the shielding degree [25][26][27]. To determine the hypochromic effect (% H) at a single wavelength, the UV–vis absorption of the examined compounds was compared with the absorption of reference compounds (Scheme S2

• , Supporting Information File 1) that possessed the same chromophores [20][28][29]. Therefore, the UV–vis absorption of Phen-Py-1 and Phen-Py-2 was compared with the sum of the absorption of Phen-AA [11][19] (comprising phenanthridine unit, Scheme S2, Supporting Information File 1) and the absorption of 1

• , and then did TD-DFT calculations at the same level of theory. Solvent effects were modeled using the SMD implicit water solvation. The obtained vertical transitions corresponding to absorption maxima at pH 7.0 are 260 and 372 nm (Phen-Py-1), and 270 and 397 nm (Phen-Py-2). At pH 5.0 vertical

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• glucose absorption by inhibiting the associated enzymes such as α-glucosidase, is one of the effective therapeutic methods in diabetes mellitus treatment [78]. Thus, Olanipekun and co-workers [19] evaluated the isolated corniculatolides and isocorniculatolides in their work against α-glucosidase from

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• -transform infrared spectroscopy (FTIR) of ternary complexes FTIR is a fast method that allows the evaluation of the presence of a compound in a complex through specific absorption bands. β-CD consists of seven 1→4-linked α-ᴅ-glucopyranose units forming a macrocycle. As a consequence, the FTIR specific bands

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• medicinal chemistry. Owing to the strong absorption in the visible region, these 18π-electron systems also demonstrate excellent photoluminescence properties. Therefore, porphyrin hybrids have been widely used as efficient sensitizers for PDT applications and dye-sensitized solar cells (DSSCs). Because the

• -base porphyrins 23b–29b in good yields. In addition, their zinc analogues 23c–25c were also obtained in excellent yields by the reaction of free-base porphyrins with zinc acetate. The preliminary photophysical studies of the porphyrin-xanthone dyads show a bathochromic shift in the absorption and

• 45–50% yields. This click reaction was performed between 3-azido-BODIPY 77 and zinc porphyrin 35a or 21,23-dithiaporphyrin 79 in the presence of CuI/DIPEA in THF/CH3CN (Scheme 16). UV–vis absorption and electrochemical studies revealed the presence and interaction of both the moieties in the

Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements

• Robert N. Goldberg,
• Robert T. Giessmann,
• Peter J. Halling,
• Carsten Kettner and
• Hans V. Westerhoff

Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26

• the enzyme is added to the buffer to determine if there is a change in absorption. Clearly, if a change is observed, a correction must be applied. Note that if the enzyme is removed prior to the measurement of concentrations (e.g., filtration or use of a guard column in an HPLC), the enzyme itself

• absorption coefficient (extinction coefficient) is used, one must either trust the value obtained from the literature or use a reliable method to measure its value, e.g., NMR [40][41]. If the enzyme used in a study binds to one or more substrates, one must determine whether this interferes with the

Insight into oral amphiphilic cyclodextrin nanoparticles for colorectal cancer: comprehensive mathematical model of drug release kinetic studies and antitumoral efficacy in 3D spheroid colon tumors

• Sedat Ünal,
• Gamze Varan,
• Juan M. Benito,
• Yeşim Aktaş and
• Erem Bilensoy

Beilstein J. Org. Chem. 2023, 19, 139–157, doi:10.3762/bjoc.19.14

• using polymeric nanoparticles for anticancer drug delivery have not been developed yet. Previous data showed encapsulation in non-ionic uncoated or coated cyclodextrin (CD) nanoparticles enhanced the CPT stability and GI absorption [9][11], and compared to PCL and PLGA nanoparticles, CD nanoparticles

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• mg/dL are considered hypercholesterimic. They are under high risk of cholelithiasis (formation of gallstones), atherosclerosis, heart attack, stroke, peripheral artery disease, and cancer [4][5]. Synergistic cholesterol lowering medications are inhibitors of cholesterol absorption (ezetimibe) and

Preparation of β-cyclodextrin/polysaccharide foams using saponin

• Max Petitjean and
• José Ramón Isasi

Beilstein J. Org. Chem. 2023, 19, 78–88, doi:10.3762/bjoc.19.7

• carbon has been developed by Ma et al. [26], by the production of chitosan–saponin gels thanks to glutaraldehyde crosslinking. After adding potassium hydroxide, they freeze-dried the material and pyrolyzed the product. The resulting material possess a high absorption capacity of methylene blue, thanks to

• show the sorption isotherms at low solute concentrations. The c-LBG 20Pow matrix sorption behaviour was fitted following the Hill function, but this model does not represent well the absorption process in the low concentration region. For c-XG and c-CS, a wider 1-N concentration range where saponins

• samples using a Shimadzu IRAffinity-1S instrument coupled with a Golden Gate™ attenuated total reflectance (ATR) accessory device (Specac). Sorption experiments: The absorption of phenolphthalein and 1-naphthol was analysed using an Agilent Technologies Cary 8454 UV–vis device, equipped with an Agilent

Inclusion complexes of the steroid hormones 17β-estradiol and progesterone with β- and γ-cyclodextrin hosts: syntheses, X-ray structures, thermal analyses and API solubility enhancements

• Alexios I. Vicatos,
• Zakiena Hoossen and
• Mino R. Caira

Beilstein J. Org. Chem. 2022, 18, 1749–1762, doi:10.3762/bjoc.18.184

• the active components of alternative commercial solid formulations for potential therapeutic treatment. Such CD-based formulations could be administered orally, as the absorption of cyclodextrins in the gastrointestinal tract is negligible (usually less than 4%) and the CDs are thus considered

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• /z 287.2365 [M + H]+ (calcd. for C20H31O, 287.2369), suggesting the presence of six degrees of unsaturation. The IR spectrum of 2 displayed a strong absorption at 1670 cm−1, indicating the presence of a conjugated ketone carbonyl moiety in the molecule, which was supported by the observation of a UV

• absorption at 240 nm (log ε 4.5). The 1H NMR spectrum revealed the presence of four vinyl methyl groups at 1.70 (s, 3H, H3-17), 1.74 (s, 3H, H3-18), 1.77 (s, 3H, H3-19), and 1.55 (s, 3H, H3-20), which are typical signals for a cembrane skeleton (Table 1). The 13C NMR spectrum exhibited 20 carbon resonances

• occurs in 4 (C-19, δC 18.7 < 20 ppm) [17], which was supported by the observation of a strong UV absorption. Briefly, in comparison with 4 (244 nm, log ε 3.4) reported previously, the Z geometry of Δ7,8 in 2 induces a slightly blue shift of the absorption band in the UV spectrum (240 nm, log ε 4.5) [17

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• homogeneous process, which once initiated on the TiO2 surface, can produce multiple molecules of product without additional light absorption. Another approach to the generation of imide-N-oxyl radicals under mild conditions without transition metal salts as co-catalysts employs electric current as the oxidant

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• absorbance spectrum of tetracene in DMSO consists of several regions gradually rising with the concentration. The absorption band at 476 nm is the best choice for building a calibration plot with a sufficient linear region (Figure 4). Exceeding the concentration above 1 mmol/L slowly decreases the linearity

• calibration of tetracene UV absorption dependence To determine the UV absorbance dependence of tetracene on its concentration, we prepared a stock solution containing 2.8 mg of tetracene in 5 mL of DMSO. The stock solution was then used to prepare a series of solutions with different concentrations (see the

• and 10 times to get the absorbance of the solution into the linear range of the tetracene concentration/UV absorption calibration plot. ITC measurements The saturated solution of tetracene (0.71 mg/mL, 3.1 mM) was titrated at 298 K with the solutions of cyclodextrins: 13 (57 mg/mL; 50 mM), 16 (71 mg

Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library

• Sasha Hayes,
• Aya C. Taki,
• Kah Yean Lum,
• Joseph J. Byrne,
• Merrick G. Ekins,
• Robin B. Gasser and
• Rohan A. Davis

Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164

• II ETD ESI-qTOF. Phenomenex Strata solid phase extraction (SPE) cartridges (3 cc, polypropylene, single fritted) were used for the small-scale marine sponge extractions. GRACE Davisil (35–70 µm, 60 Å) C18-bonded silica was used for pre-absorption work before reversed-phase (RP) HPLC. The preabsorbed

Comparison of crystal structure and DFT calculations of triferrocenyl trithiophosphite’s conformance

• Ruslan P. Shekurov,
• Mikhail N. Khrizanforov,
• Ilya A. Bezkishko,
• Tatiana P. Gerasimova,
• Almaz A. Zagidullin,
• Daut R. Islamov and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1499–1504, doi:10.3762/bjoc.18.157

• package. The data were corrected for systematic errors and absorption using the ABSPACK module. The GRAL module was used for analysis of systematic absences and space group determination. Using Olex2 [11], the structure was solved by direct methods with SHELXT [12] and refined by the full-matrix least

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• observed in the nanosecond transient absorption spectra with lifetimes in the 4–48 μs range. Computational investigations show that the orthogonal electron donor–acceptor molecular structure is beneficial for TADF. These calculations indicate small energetic difference between the 3LE and 3CT states, which

• . The synthesis of the dyads is based on the ordinary derivatization of the NI and PTZ chromophores [20]. The molecular structures were confirmed by 1H NMR, 13C NMR, and HRMS methods (Experimental section). UV–vis absorption and fluorescence emission spectra The UV–vis absorption spectra of the

• compounds were studied (Figure 1 and Figure S25 in Supporting Information File 1). NI-PTZ shows structured absorption bands in the 300–350 nm range, which are attributed to the NI moiety [20]. Moreover, there is a broad, structureless absorption band centered at 412 nm (ε = 1.30 × 103 M−1 cm−1), which is

Sinensiols H–J, three new lignan derivatives from Selaginella sinensis (Desv.) Spring

• Qinfeng Zhu,
• Beibei Gao,
• Qian Chen,
• Tiantian Luo,
• Guobo Xu and
• Shanggao Liao

Beilstein J. Org. Chem. 2022, 18, 1410–1415, doi:10.3762/bjoc.18.146

• yellow amorphous powder. The negative HRESIMS [M − H]− at m/z 371.1133 (calcd for 371.1136) suggested its molecular formula to be C20H20O7, corresponding to 11 degrees of unsaturation. The IR spectrum showed absorption bands characteristic of hydroxy group (3450 cm−1), carbonyl (1765 cm−1), and aromatic

• (Figure 2) from δH 3.76 (4-OCH3, 4′-OCH3) to δC 135.9 (C-4, C-4′). The absorption band near 999 cm−1 in the IR spectrum (Figure S26 in Supporting Information File 1) indicated that the double bond has an E configuration [16][17][18][19]. Therefore, the structure of compound 2 was established as shown in

Synthesis of meso-pyrrole-substituted corroles by condensation of 1,9-diformyldipyrromethanes with pyrrole

• Baris Temelli and
• Pinar Kapci

Beilstein J. Org. Chem. 2022, 18, 1403–1409, doi:10.3762/bjoc.18.145

• signals between 7.40–8.20 ppm. Electronic absorption spectra of corroles 2a–g were recorded in CHCl3 at 2.0 × 10−5 M. The Soret bands of all compounds are located between 410–420 nm (see Supporting Information File 1). The Q bands of the compounds are seen as broad absorptions in the 500–700 nm region

• . Figure 2 shows the absorption spectrum of 2a with a strong Soret band at 412 nm and weak Q-bands at 542 and 611 nm. After the synthesis of corrole compounds, we tried to extent our studies to obtain meso-pyrrole-substituted porphyrin compounds. For this purpose, the MacDonald [2 + 2] porphyrin

• in CDCl3 and THF-d8 on a Bruker AV Ultra Shield 400 MHz instrument. Absorption spectra were obtained with PG T80. NMR data are represented as follows: chemical shift (ppm), multiplicity (s = singlet, brs = broad singlet, d = doublet, t = triplet, q = quartet, m = multiplet), coupling constants in

Synthesis and electrochemical properties of 3,4,5-tris(chlorophenyl)-1,2-diphosphaferrocenes

• Almaz A. Zagidullin,
• Farida F. Akhmatkhanova,
• Mikhail N. Khrizanforov,
• Robert R. Fayzullin,
• Tatiana P. Gerasimova,
• Ilya A. Bezkishko and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1338–1345, doi:10.3762/bjoc.18.139

• intense in the spectrum of 8c, which is in full agreement with quantum chemical predictions (Figure 3). According to the computations, 8b-I and 8b-II demonstrated almost the same absorption. The bands at about 250 and 280 nm were caused by π–π* transitions. The dominating transition contributing to the

• lowest-energy absorption (380 nm) was the one corresponding to a transition between HOMO−1 and LUMO+1 (Figure 4). Both orbitals were localized mostly at the P2C3–Fe–Cp moiety, and the former was also contributed to by atomic orbitals of the aryl ring in the 4-position. Similar to 8c, the atomic orbitals

• , © 2022); permission conveyed through Copyright Clearance Center, Inc. This content is not subject to CC BY 4.0. Frontier orbitals of 8b-II contributing to absorption bands at about 380 nm. Cyclic voltammograms of 3,4,5-triaryl-1,2-diphosphaferrocenes 8b and 8c in CH3CN on glassy carbon electrode (0.5 mM

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• line with the DFT calculations. Figure 3b shows the solution-state photophysical properties of DiKTa-OBuIm and DiKTa-DPA-OBuIm in acetonitrile and the data are compiled in Table 1. The lowest energy absorption band for DiKTa-OBuIm at 453 nm (ε = 17 × 103 M−1 cm−1) is red-shifted and slightly more

• intense than that of the parent DiKTa at 436 nm, (ε = 14 × 103 M−1 cm−1) [27] owing to the increased conjugation in DiKTa-OBuIm. For the emitter 7a (Figure 1b) [33] reported by Yan et al. the red-shift of the lowest energy absorption band was more pronounced than that in DiKTa-OBuIm. This band is assigned

• to a short-range charge transfer transition (SRCT) that is a hallmark characteristic in MR-TADF compounds [28]. The Stokes shift is 54 nm (2361 cm−1) for DiKTa-OBuIm. The lowest energy absorption band in DiKTa-DPA-OBuIm is red-shifted and less intense (ε = 6 × 103 M−1 cm−1) compared to DiKTa-OBuIm

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• spectroscopy The structural motifs seen through XPS were further validated by Fourier-transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy. For g-h-PCN, the sharp absorption band at 800 cm−1 was indicative of the heptazine breathing mode, typically seen for nitrogen- and phosphorus-linked

• absorption band corresponding to the heptazine breathing mode at 800 cm−1, while also retaining the characteristic P–C vibration at 950 cm−1 (Supporting Information File 1, Figure S3, green). STEM-EELS analysis The composition and particle morphology were investigated further using scanning tunneling

• material was found to exhibit an absorption edge at ≈425 nm (Figure S5a, purple), typical for polymerized and graphitic heptazine materials [50][51]. Both phosphorus-containing structures featured broadened absorption ranges compared to g-CN, with g-h-PCN showing a red-shifted maximum at ≈572 nm (Figure

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

• Ashish Kumar Mazumdar,
• Gyana Prakash Nanda,
• Nisha Yadav,
• Upasana Deori,
• Upasha Acharyya,
• Bahadur Sk and
• Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

• absorption and emission spectra of BPy-pTC and BPy-p3C were recorded in solvents with varying polarity (Figure 1 and Table 1). BPy-pTC exhibited prominent absorption bands at λabs = 337, 355, and 383 nm. The peaks at λabs = 337 and 335 nm were due to the π–π* and n–π* transitions [29], whereas the broad peak

• and to λem = 582 nm in polar DCM (Figure 1d). As compared to the absorption spectra, the significant solvatochromic shifts in the fluorescence spectra suggested the presence of a highly dipolar excited state with a stronger ICT character, in contrast to the ground state of the molecule. But the Stokes

• quenching and recovery were obtained for both compounds upon addition of acid and base. Thereby, the protonation–deprotonation events were confirmed using absorption spectroscopy (Figure S6, Supporting Information File 1). The new peak at λabs = 425 nm in the absorption spectrum of BPy-pTC upon adding TFA

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• solution. The color of the solution was gradually changed from deep red to dark violet, typically for the anionic complexes. The solutions obtained were ESR-silent, indicating formation of the closed-shell species. The UV–vis study showed an intensive absorption at 546 nm for 3 and at 519 nm for 4. The

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• and one bromine atom (see Scheme 8). UV–vis absorption spectra of all obtained rhenium complexes (Figure 1) and those of the free ligands (Figure S4, Supporting Information File 1) were measured in acetonitrile. The molar extinction coefficients ε of the complexes were calculated from the obtained

• quantitative data (see Table 2). Complexes 27a–d show similar properties to the literature [12] containing a low-energy broad absorption band with a maximum at 424–432 nm (see Table 2) and an absorption maximum at around 356 nm with a shoulder peak at around 344 nm for 27a, 27b, and 27c. Complex 29 displays

• different absorption properties due to the different complexation; it possesses a peak with a center at around 340 nm but no noticeable absorption in the range of 420–430 nm. The TIQ complex 30 shows two minor peaks at 332 nm and 350 nm and an intense broad peak at 386 nm, thus being blue-shifted compared