Synthesis and characterization of inner-sphere substitution products in azide-containing сobalt(III) dioximates

New compounds of Co(III) dimethylglyoximate with the sulfanilamide derivative [Co(N₃)(DmgH)₂(SAM)] (DmgH^– is the dimethylglyoxime monoanion, and SAM is–NH₂–C₆H₄–SO₂–NH–R) are synthesized using the structural block [Co(N₃)(DmgH)₂(Н₂О)] as the initial one. The reaction products of various [Co(N₃)(DmgH)₂(SAM)] with ligand L (L is pyridine (Py), thiourea (Thio), triphenylphosphine (PPh₃), nicotinamide (Nia), iso-nicotinamide (INia), isonicotinic acid (НINА), 4-pyridinaldoxime (4-PaoH), 4,4’-bipyridine (Bipy), and NH₄NCS) are synthesized. The compounds are studied by IR and NMR spectroscopy and X-ray diffraction analysis (CIF files CCDC 1414767–1414775 (I, V–XII)). The following facts are established. First, only the coordinated water molecule in [Co(N₃)(DmgH)₂(Н₂О)] is replaced by SAM. Second, SAM from different similar compounds also undergoes substitution by the aforementioned organic ligands. The exception is the compound obtained by the reaction of [Co(N₃)(DmgH)₂(SAM)] with NH₄NCS, due to which the NCS^– anion replaces both SAM and inorganic anion N ₃ ^- . The X-ray diffraction analysis shows that the substitution reactions give both mononuclear compounds [Со(N₃)(DmgH)₂(Py)], [Со(N₃)(DmgH)₂(PPh₃)], [Со(N₃)(DmgH)₂(Thio)], [Со(N₃)(DmgH)₂(Nia)] [Со(N₃)(DmgH)₂(INia)], [Со(N₃)(DmgH)₂(HINА)] ? H₂O, [Со(N₃)(DmgH)₂(4-PaoH)] ? DMF, and [Со(N₃)(DmgH)₂(Bipy)] and binuclear molecular complexes [(Со(N₃)(DmgH)₂)₂(Bipy)] ? 0.5H₂O and [(Со(N₃)(DmgH)₂)₂(Bipy)] ? H₂O, as well as ionic complex (NH₄)[Co(SCN)₂(DmgH)₂] ? 3H₂O. The obtained compounds supplement a series of complexes that make it possible to evaluate the trans effect of the N ₃ ^- anion on the bond lengths along the axial coordinate and on the Со–N bonds in the equatorial plane of the octahedron.     

Stabilisation of a heptamethine cyanine dye by rotaxane encapsulation

The crystal structure of a cyanine dye rotaxane shows that the cyclodextrin is tightly threaded round the polymethine bridge of the dye; encapsulation dramatically increases the kinetic chemical stability of the radicals formed on oxidation and reduction of the dye, making it possible to observe the rotaxane radical dication by ESR and UV-vis-NIR spectroscopy.     

Physicochemical characterization of sanguinarine-hydroxypropyl-β-cyclodextrin binary and ternary systems

Complexation of sanguinarine with hydroxy-propyl-β-cyclodextrin (HPβCD) in the presence and absence of hydrophilic polymer—polyvinylpyrrolidone K30 was studied. Respective binary and ternary systems were prepared using two techniques, physical mixture and lyophilization, and characterized by FT-infrared spectrometry, differential scanning calorimetry and X-ray diffractometry. The Fourier Transform Infrared spectra of the lyophilized binary and ternary systems showed significant shifts in the regions of 1240–1300 cm^?1, 1450–1525 cm^?1 and 1600–1650 cm^?1, where absorptions of –C–O–C– asymmetrical stretching of sanguinarine rings A and F and ν_C=C ring vibrations of sanguinarine benzo[c]phenanthridine system can be observed respectively. Moreover, in the case of ternary products ν_C=O amide band absorption of polyvinylpyrrolidone (1600–1750 cm^?1) shifted to the lower wavenumbers in both the physical mixture and the lyophilized product. These changes in the spectra of the studied systems proved the involvement of the respective molecular groups in complexation process. Differential scanning calorimetry and X-ray diffractometry indicated different states of drug amorphization and entrapment in HPβCD in the presence and without polyvinylpyrrolidone. The obtained results let us conclude that obtained binary and ternary systems represent sanguinarine-HPβCD molecular complexes, with different rate of inclusion in the presence and without polyvinylpyrrolidone.     

A Biomimetic Synthesis of Sacculatane Diterpenoids

The biomimetic synthesis of sacculatane‐type epimeric compounds 14a and 14b is reported. The key synthetic step is the low‐temperature superacidic cyclization of (all‐E)‐ω‐acetoxygeranylgeraniol 12 obtained in nine steps from geranyllinalool ( 13 ). The 19‐acetoxysacculata‐7,17‐dien‐11‐ol ( 14a ) could be an important and convenient starting compound for the synthesis of other sacculatane diterpenoids.     

The Impact of Molecular Orientation on the Photovoltaic Properties of a Phthalocyanine/Fullerene Heterojunction

The anisotropy inherent to many planar organic molecules leads to a high sensitivity of various fundamental processes to the orientation of molecules within films and at heterojunctions. Such processes include absorption, charge and exciton transport, energy levels, and charge transfer, all of which are critical to organic solar cell operation. Here,an in‐depth study of bilayer cells consisting of a donor/acceptor interface between zinc phthalocyanine (ZnPc) and fullerene (C₆₀) is conducted and devices with the typically deposited standing up (edge‐on) orientation are compared to those with ZnPc lying flat (face‐on). The face‐on ZnPc‐based device allows for an increase in all solar cell parameters, substantially increasing power conversion efficiency from 1.5% to 2.8%. Spectrally resolved photocurrent measurements reveal a >50% increase in ZnPc signal, from which only 12% is accounted for by the increase in absorption associated with the face‐on orientation. The increase in internal quantum efficiency is accounted for via an improved charge transfer. The results of this study indicate that proper consideration of the orientation between donor and acceptor needs to be taken in order to fully optimize the numerous processes required for photovoltaic energy conversion.     

Tuning delocalization in the radical cations of 1,4-bis[4-(diarylamino)styryl]benzenes, 2,5-bis[4-(diarylamino)styryl]thiophenes, and 2,5-bis[4-(diarylamino)styryl]pyrroles through substituent effects

Radical cations have been generated for 10 bis[4-(diarylamino)styryl]arenes and heteroarenes to investigate the effect of the electron-richness of the terminal groups and of the bridging (hetero)arene on delocalization. The intervalence charge-transfer bands of these radical cations vary from weak broad Gaussians, indicative of localized class-II mixed-valence species, to strong relatively narrow asymmetric bands, characteristic of delocalized class-III bis(diarylamino) species, to narrow symmetric bands in cases where the bridge contribution to the singly occupied molecular orbital is largest. Hush analysis of these bands yields estimates of the electronic coupling varying from 480 cm(-1) (electron-poor bridge, most electron-rich terminal aryl groups) to 1000 cm(-1) (electron-rich bridge, least electron-rich termini) if the diabatic electron-transfer distance, R(ab), is equated to the N-N separation. Computational and electron spin resonance (ESR) evidence for displacement of the diabatic states into the bridge (reduced R(ab)) suggests that these values are underestimates and that even more variation is to be expected through the series. Several dications have also been studied. The vis-NIR absorption of the dication of (E,E)-1,4-bis{4-[bis(4-n-butoxyphenyl)amino]styryl}-2,5-dicyanobenzene is seen at an energy similar to that of the strongest band in the spectrum of the corresponding weakly coupled monocation, with approximately twice the absorptivity, and its ESR spectrum suggests essentially noninteracting radical centers. In contrast, the electronic spectra of class-III monocations show no clear relationship to those of the corresponding dications, which ESR reveals to be singlet species.     

Isolation and crystal structures of two singlet bis(triarylamine) dications with nonquinoidal geometries

We report the first structural data for bis(diarylamine) "bipolarons": we have isolated and crystallographically characterized salts of the dications obtained by two-electron oxidation of E-4,4'-bis[di(p-anisyl)amino]stilbene and E,E-2,5-bis{4-[di(p-anisyl)amino]styryl}-3,4-di(n-butoxy)thiophene, [1](2+) and [2](2+) respectively. ESR, NMR, and magnetometry suggest both species have singlet ground states. X-ray structures, together with (1)H NMR coupling constants for [2](2+), indicate geometries in which the bond lengths are shifted toward a quinoidal pattern relative to that in the neutral species, but not to a fully quinoidal extent. In particular, the bond-length alternations across the vinylene bridging groups approach zero. DFT calculations with closed-shell singlet configurations reproduce the observed structures well. Our results indicate that singlet species for which one might expect quinoidal geometries (with differences of ca. 0.1 A between formally single and double bonds) on the basis of a limiting valence-bond representation of the structure can, in fact, show structures with significantly different patterns of bond lengths.     

Probing charge transport in pi-stacked fluorene-based systems

The molecular parameters governing charge transport along a pi-stacked fluorene chain in poly(dibenzofulvene) are studied by a joint experimental and theoretical approach involving high-resolution gas-phase photoelectron spectroscopy and quantum-mechanical methods. We specifically investigate the electronic couplings between fluorene moieties as well as the intramolecular reorganization energies, for both holes and electrons. Our results indicate that a pi-stacked fluorene chain favors hole transport over electron transport. The values for electronic couplings and reorganization energies estimated here are compared with those derived recently for pentacene.     

Hexaazatriphenylene (HAT) versus tri‐HAT: The Bigger the Better?

A new hexaazatriphenylene (HAT) derivative formed by the fusion of three HAT units has been prepared and its electronic and molecular structures have been fully characterized by optical and vibrational Raman spectroscopy, electrochemistry, solid-state UV and inverse photoemission spectroscopy (UPS and IPES), and by quantum-chemical calculations. A comparative HAT versus tri-HAT study was performed. The fusion of three HAT molecules causes modifications in the optical and electrochemical properties consistent with enhanced π-electron delocalization attained in a bigger planar core. Such combined experimental and theoretical studies are useful to balance chemical design with supramolecular engineering directed to find enhanced characteristics for new organic semiconductor applications.     

New Сu(II) and Co(II) Complexes with 2-Benzoylpyridine: Syntheses and Crystal Structures

Russian Journal of Coordination Chemistry - Two new mononuclear complexes [Cu(Bzpy)2(Cl)2] (I) and [Cо(Bzpy)2(H2O)2](BF4)2 (II) are synthesized by the reactions of 2-benzoylpyridine (Bzpy)...