Copper(II) bisimidazolate affords five different polymorphs; of these, one was structurally characterized 40 years ago by standard single-crystal X-ray diffraction (Jarvis, J. A. J.; Wells, A. F. ...Acta Crystallogr. 1960, 13, 1027), while the remaining four, selectively prepared as pure polycrystalline phases, have been now studied by X-ray powder diffraction (XRPD) methods. Of the four new (blue, green, olive-green, and pink) phases, three were solved by the ab initio XRPD technique and refined by the Rietveld method, and the fourth phase (pink) could not be structurally characterized. Crystal data for Cu(imidazolate)2 n : blue phase, a = 27.559(3) Å, c = 5.3870(9) Å, trigonal, R3̄, Z = 54; green phase, a = 21.139(1) Å, b = 19.080(1) Å, c = 9.2842(8) Å, orthorhombic, Ccca, Z = 20; olive-green phase, a = 11.7556(8) Å, b = 23.422(2) Å, c = 9.0727(9) Å, β = 104.993(5)°, monoclinic, C2/c, Z = 12. All polymorphs contain four-coordinate CuN4 chromophores and (N,N‘)-exobidentate imidazolate ligands, but show different spectroscopic and structural properties, the latter ranging from 2D to different 3D networks of the PtS, sodalite, and moganite archetypes. The intermediacy of the Cu(imidazole)2CO3·H2O species in the synthesis of the blue polymorph has been confirmed by spectroscopic and thermal analyses. FTIR, Raman, and electronic spectra were correlated with the structural features revealed in the present work, and used to gain insight into the coordination geometry of copper(II) ions of the pink polymorph. In addition, the correct Raman spectrum for copper(II) bisimidazolate, common for all polymorphs, has been definitely determined.
The second-order nonlinear optical (NLO) properties of two tetrathiafulvalene (TTF)-fused electron donor-acceptor dyads have been determined using the Electric Field Induced Second Harmonic ...generation (EFISH) technique and theoretically rationalized. Dyads TTF-dppz (1) and TTF-BTD (2) were obtained by direct fusion of a TTF electron donor unit either with a dipyrido3,2-a:2',3'-cphenazine (dppz) or a benzothiadiazole (BTD) electron acceptor moiety. Dyad 1 acts as a reversible acido-triggered NLO switch by protonation/deprotonation at two nitrogen atoms of the dppz acceptor moiety induced by sequential exposure to HCl and ammonia vapors. Dyad 2, on the other hand, displays redox-tunable NLO properties upon two consecutive oxidations to its radical cation 2+˙ and dication 22+ species. The resulting final dication 22+ exhibits an inversion of the sign of β
, due to a completely inverted distribution of the frontier molecular orbitals with respect to those of its neutral species, leading to a scarcely polar species in the excited state, as indicated by the theoretical calculations.
The unexpected and acido-triggered reversible luminescence and nonlinear optical properties of (2-pyrene-1-yl-vinyl)pyridine, a simple and highly transparent chromophore, are studied both in solution ...and in the solid state. Remarkably, for the first time the acidomodulation of the NLO response of a poled thin film is reported.
The combination of continuum and ultrafast pump-probe spectroscopy with DFT and TDDFT calculations, in viscous and non-viscous environments, is effective in unraveling important features of the ...twisted intramolecular charge transfer mechanism in a new push-pull molecule that possesses aggregation induced emission properties. Long-living optical gain is found when this mechanism is inhibited, highlighting the importance of the environment rigidity in the design of materials for photonic applications.
Huge second harmonic generation (SHG) activityis displayed by the new hybrid inorganic–organic material DAMS*Cu5I6 (see Figure). Ab‐initio XRPD structure determination explains this through the ...presence of cationic guest J‐aggregates between Cu‐defective anionic host CuI slabs. Thermal stability and thin‐film suitability make the material technologically interesting.
Novel D–π–A push–pull chromophores were synthesized in good yields by CuAAc coupling of 4-X-2,3,5,6-tetrafluorophenyl-1-azides (X = H, Br, I) with 4-ethynyl-dimethylaniline. Thanks to the ...self-complementary binding sites at the molecular ends, the iodo derivative self-organizes in the solid state forming head-to-tail halogen-bonded one-dimensional unlimited chains. The second-order NLO properties of the iodo compound have been investigated by the solution-phase electric field induced second-harmonic generation method (EFISH).
Inorganic–organic hybrid materials have shown excellent optoelectronic device performances from single-layer solution-processed thin films. Their electronic bands are coupled to the ionic ...interactions within the organic and inorganic moieties. Exactly these features also allow a sequential deposition route so as to implement thin films having inherently non-linear optical properties perpendicular to the substrate plane. Here, we demonstrate a sequential layer-by-layer path to prepare films of an inorganic–organic hybrid material DAMSCu 5 I 6 through a self-recognition process in the solid state between the first CuI layer and the successive DAMSI layer. A persistent non-linear optical behavior, typical of oriented films, is consequently accessible on different substrates without electrical bias poling through the excellent self-recognition of dipoles aligned along the z -axis. In addition, semiconductive and preliminary photovoltaic properties of the film are observed. This work highlights all aspects of the solution-based films with potential to serve as versatile and robust optoelectronic active materials.
For fluorescent compounds, the combined use of absorption and emission solvatochromic data allows to estimate indirectly the cavity radius of the molecule in solution, a very critical parameter in ...the application of the solvatochromic method for the determination of the quadratic hyperpolarizability
β of dipolar molecules. For two test compounds,
trans-4-4-(dimethylamino)styrylpyridine (DASP) and 5-dimethylamino-1,10-phenanthroline (DAPHEN), the
β values so obtained are compared with those obtained by the EFISH (Electric Field Induced Second-Harmonic generation) technique. For DAPHEN, the versatility of the method described in this work in the presence of more than one electronic transition contributing to the non-linear optical response is demonstrated.
This study evaluated the prenatal diagnosis of Turner syndrome by ultrasound examination in an unselected population from all over Europe. Data from 19 congenital malformation registries from 11 ...European countries were analyzed. Turner syndrome was diagnosed in 125 cases (7.2%) in a total of 1,738 chromosome abnormalities. Sixty-seven percent of cases were detected prenatally by ultrasound examination due to the presence of congenital defects. The most frequent anomalies were cystic hygroma (59.5%) and hydrops fetalis (19%). The most frequent karyotype was 45,X (81.6%) followed by different types of mosaicism (16.8%). Significant differences in congenital defects (P = 0.0003) were observed between 45,X karyotypes and 45,X mosaicism cases. Prenatal counseling for 45,X mosaicism should take into account the expectation of a milder phenotype. In 78.6% of cases diagnosed by ultrasound examination due to congenital anomalies, the pregnancy was terminated. Prenatal detection of Turner syndrome by ultrasound examination was high in this unselected population.
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