Mehmet Menaf Ayhan

ABAB homoleptic bis(phthalocyaninato)lutetium(III) complex: toward the real octupolar cube and giant quadratic hyperpolarizability.

The concept of octupolar molecules has considerably enlarged the engineering of second-order nonlinear optical materials by giving access to 2D and 3D architectures. However, if the archetype of octupolar symmetry is a cube with alternating donor and acceptor groups at the corners, no translation of this ideal structure into a real molecule has been realized to date. This may be achieved by designing a bis(phthalocyaninato)lutetium(III) double-decker complex with a crosswise ABAB phthalocyanine bearing alternating electron-donor and electron-acceptor groups. In this communication, we present the first step toward this goal with the synthesis, crystal structure determination, and measurement of the molecular first-order hyperpolarizability β by harmonic light diffusion, of an original lutetium(III) sandwich complex displaying the required ABAB-type alternation for one face of the cube. This structure is characterized by an intense absorption in the near-IR due to an intervalence transition and exhibits the highest quadratic hyperpolarizability ever reported for an octupolar molecule, √ = 5750 × 10(-30) esu.

Correction to “Comprehensive Synthesis of Monohydroxy–Cucurbit[n]urils (n = 5, 6, 7, 8): High Purity and High Conversions”

During our follow-up work on the conjugation of monohydroxylated cucurbiturils, we found that the reported yields of monohydroxylation of CB[n] (n = 5−8), 90−95%, were incorrect. This was due to the misleading composition of the crude product, with an approximate 0.3/0.3/0.3 ratio of CB[n], CB[n]−(OH)1, and CB[n]−(OH)2, giving NMR signal integrals and peak positions that match the expected values for pure CB[n]−(OH)1. After purification of the product via silica column chromatography using water/acetic acid/formic acid as eluent, the corrected yields are 5−37% for CB[n]− (OH)1, with n = 5−8. These results were confirmed by repeated experiments starting with 100 mg, and using up to 3 g, of CB[n]. The Supporting Information has been revised to include MS spectra of pure CB[n]−(OH)1 and details of the column chromatography purification procedure for all CB[n]−(OH)1. Page 10238. The title should be revised to Comprehensive Synthesis of Monohydroxy−Cucurbit[n]urils (n = 5, 6, 7, 8). Page 10238. In the Abstract, the 95−100% conversion reported for CB[n]−(OH)1 should be corrected to 20−40%, depending on the CB[n] considered. Scale-up experiments were performed using up to 3 g of CB[n] with quartz reactors of 50 or 300 mL. Page 10239. In the Synthesis section, the conversions given in the text and in Table 1 are incorrect due to the misleading H NMR spectra, and should actually be 20−40%. The values in Table 1 are thus apparent conversions determined by H NMR. Isolated yields have been determined and are given in the revised Supporting Information (5−37% for the CB[n]− (OH)1 series). Page 10242. In Table 3, likewise, the conversion of CB[8] toward the formation of CB[8]−(OH)1 is an apparent conversion determined by H NMR, where CB[8] is transformed to CB[8]−(OH)1 and CB[8]−(OH)2. Thus, the title of the table should be revised to “Apparent Conversion of CB[8] toward the Formation of CB[8]−(OH)1”. ■ ASSOCIATED CONTENT *S Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.6b00188. Procedure for the preparation of CB[n]−(OH), C NMR spectra, details of high resolution MS analyses, decay products of CB[8], details for the calculations of BDEs, and structures of each CB[n]· radical (revised) (PDF)

ABAB homoleptic bis(phthalocyaninato)lanthanide(III) complexes: original octupolar design leading to giant quadratic hyperpolarizability.

The octupolar cube, a Td symmetry cube presenting alternating charges at its corners, is the generic point charge template of any octupolar molecule. So far, transposition into real molecular structures has yet to be achieved. We report here a first step toward the elaboration of fully cubic octupolar architectures. A series of octupolar bis(2,3,16,17-tetra(hexylthio)phthalocyaninato)lanthanide double-decker complexes [Pc2Ln], Ln = Nd (1), Eu (2), Dy (3), Y (4), and Lu (5), are described, whose original three-dimensional structures display the required alternation of ABAB type for one face of the cube and the delocalization between the two rings approximating to the electronic interaction along the edges of the cube. Synthesis, X-ray crystal structure, and study of the optical properties and of the first molecular hyperpolarizability β are reported. The size of the lanthanide (III) central ion modulates the ring-to-ring distance and the degree of coupling between the two phthalocyanine rings. As a consequence, the optical properties of these octupolar chromophores and in particular the strong near-infrared absorption due to the intervalence transition between the two rings also depend on the central lanthanide (III) ion. The first oxidized and reduced states of the complexes, while keeping a similar octupolar structure, display considerably changed optical properties compared to the neutral states. Second-order nonlinear properties were determined by nonpolarized harmonic light scattering in solution at 1907 nm. Exceptionally large dynamic molecular first hyperpolarizabilities √(1907), among the highest ever reported, were found that showed a strong dependence on the number of 4f electrons.

Optical properties of a visible push-pull chromophore covalently bound to carbohydrates: solution and gas-phase spectroscopy combined to theoretical investigations.

The use of visible absorbing and fluorescent tags for sensing and structural analysis of carbohydrates is a promising route in a variety of medical, diagnostic, and therapeutic contexts. Here we report an easy method for covalent attachment of nonfluorescent push-pull chromophores based on the 4-cyano-5-dicyanomethylene-2-oxo-3-pyrroline ring to carbohydrate moieties. The impact of sugar grafting on the optical properties of the push-pull chromophore in the gas phase and in solution was investigated by absorption and action spectroscopy and theoretical methods. The labeled sugars efficiently absorb photons in the visible range, as demonstrated by their intense photodissociation in a quadrupole ion trap. A strong blue shift (-70 nm) of the gas-phase photodissociation intensity maximum is observed upon sugar grafting, whereas no such effect is visible on the solution absorption spectra. Molecular dynamics simulations of labeled maltose in the gas phase describe strong interactions between the sulfonated chromophore and the carbohydrate, which lead to cyclic conformations. These are not observed in the simulations with explicit solvation. Time-dependent density functional theory (TD-DFT) calculations on model molecules permit us to attribute the observed shift to the formation of such cyclic conformations and to the displacement of the negative charge relative to the aromatic moiety of the chromophore.

Mechanism of the Zn(II)Phthalocyanines’ Photochemical Reactions Depending on the Number of Substituents and Geometry

In this work, the synthesis and the nonlinear absorption and population dynamics investigation of a series of zinc phthalocyanines (ZnPcs) dissolved in chloroform are reported. In order to determine the relevant spectroscopic parameters, such as absorption cross-sections of singlet and triplet excited states, fluorescence relaxation times, intersystem crossing, radiative decay and internal conversion, different optical and spectroscopic techniques were used. By single pulse and pulse train Z-scan techniques, respectively, singlet and triplet excited states‘ absorption cross-section were determined at 532 nm. Furthermore, the intersystem crossing time was obtained by using both techniques combined with the fluorescence lifetime determined by time-resolved fluorescence. The radiative and internal conversion rates were determined from the fluorescence quantum yield of the samples. Such spectroscopy parameters are fundamental for selecting photosensitizers used in photodynamic therapy, as well as for many other applications.

Halogen bonding driven crystal engineering of iodophthalonitrile derivatives

The nature of halogen bonds (XBs) depending on the number and position of the XB donor (I) and acceptor (CN) groups in iodophthalonitrile derivatives such as 4-iodo-phthalonitrile (2a), 3-iodo-phthalonitrile (2b), 4,5-diiodo-phthalonitrile (2d) and 3,4-diiodo-phthalonitrile (2c) as well as in para-, ortho- and meta-iodo-substituted benzonitriles (1a–1c) was studied by X-ray analysis and ab initio calculations. Density functional theory (DFT) and the Boltzmann transport equation have been applied to calculate the semi-classical thermoelectric transport properties of the crystalline compounds of 1a–1c, 2a–2d. In 2a–2c, the molecules are consolidated into 2-D networks while in 2d the triple helix spiral staircase structure is formed due to XBs where the unusual bifurcated asymmetric XBs were observed. The Seebeck coefficients of all the studied organic semiconductors were significantly positive, suggesting that the hole-type carriers dominate the thermoelectric transport.

Chameleonic Dye Adapts to Various Environments Shining on Macrocycles or Peptide and Polysaccharide Aggregates

This work describes latent fluorescence particles (LFPs) based on a new environmentally sensitive carbazole compound aggregated in water and their use as sensors for probing various cavitands and the different stages of aggregating systems. Cyclodextrins (CDs), cucurbit[n]urils (CB[n], n = 6, 7, 8), and a resorcinarene capsule were used to study the dynamic nature of the LFPs. The fluorescence was dramatically enhanced by a proposed disaggregation-induced emission enhancement (DIEE) mechanism with specific features for CB[n]. Then, the aggregated states of the dipeptides Leu-Leu, Phe-Phe, and Fmoc-Leu-Leu (vesicles, crystals, fibers) were studied by fluorescence spectroscopy and confocal fluorescence microscopy thanks to the adaptive and emissive behavior of the LFPs, allowing us to study an interesting polymorphism phenomenon. The LFPs have then been used in the sensing of the aggregation of the polysaccharide alginate, for which distinct fluorescence turn-on is detected upon stepwise biopolymer assembly, and for amylose detection. The carbazole particles not only adapt to various environments but also display multicolor fluorescent signals. They can be used for the fast probing of the aggregation propensity of newly prepared molecules or biologically relevant compounds or to accelerate the discovery of new macrocycles or of self-assembling peptides in water.

Optimized synthesis and crystal growth by sublimation of 1,3,3-trichloroisoindolenines, key building blocks for crosswise phthalocyanines

Among possible asymmetrically substituted phthalocyanines, ABAB derivatives remain rare. Their selective synthesis is based on the use of trichloroisoindolenines, so far remaining tedious to obtain. An optimized synthesis of 1,3,3-trichloroisoindolenine 1 and 1,3,3,6,7-pentachloroisoindolenine 2 is reported. An original crystallization method based on crystal growth by sublimation was eminently suitable regarding the air-sensitivity of these derivatives and allowed their thorough crystallographic characterization.