The zwitterionic 1,1′-bis(4-carboxyphenyl)-4,4′-bipyridinium (bp4pc) has been synthesized and crystals of its hydrated form bp4pc·2H 2 O and of its protonated reduced form H-bp4pc have been obtained. Upon heating, bp4pc·2H 2 O undergoes partial dehydration, leading to bp4pc·H 2 O at 160°C, together with a color change from yellow (room temperature) to green (140°C) and finally to brown (160-180°C). Analysis of bond lengths in the solid state reveals the expected short (d = 1.425 Å) and long (d = 1.485 Å) C-C central bond lengths in the all-radical salt H-bp4pc and bp4pc·2H 2 O, respectively, whereas the distance of 1.475 Å in bp4pc·H 2 O does not allow a conclusion to be drawn regarding the presence of radicals in this com-[a] MOLTECH

We show how to record and analyze solid-state NMR spectra of organic paramagnetic complexes with moderate hyperfine interactions using the Cu-cyclam complex as an example. Assignment of the (13)C signals was performed with the help of density functional theory (DFT) calculations. An initial assignment of the (1)H signals was done by means of (1)H-(13)C correlation spectra. The possibility of recording a dipolar HSQC spectrum with the advantage of direct (1)H acquisition is discussed. Owing to the paramagnetic shifting the resolution of such paramagnetic (1)H spectra is generally better than for diamagnetic solid samples, and we exploit this advantage by recording (1)H-(1)H correlation spectra with a simple and short pulse sequence. This experiment, along with a Karplus relation, allowed for the completion of the (1)H signal assignment. On the basis of these data, we measured the distances of the carbon atoms to the copper center in Cu-cyclam by means of (13)CR2 relaxation experiments combined with the electronic relaxation determined by EPR.

We have acquired 1H and 13C solid-state NMR (ssNMR) spectra of the paramagnetic Cu(II)-2-pyrazine-carboxylate (Cu-Py) complex and assigned paramagnetic 1H/13C signals using density functional theory (DFT) calculations. The unpaired electron in Cu(II) ionexacerbates the 1H and 13C chemical shifts in the Cu-Py complex through hyperfine interactions, making the conventional NMR signal assignment non-feasible. Further, the nuclear fast relaxation in paramagnetic metal-organic system hampers application of routine ssNMR techniques for signal acquisition. In our work we have employed simple DEPTH experiment at 50 kHz magic angle spinning (MAS) for acquiring 1H and 13C 1D ssNMR spectra of the paramagnetic Cu(II)-2-pyrazine-carboxylate (Cu-Py) complex. The paramagnetic augmented (diamagnetic chemical shift + paramagnetic shift) 1D 1H and 13C ssNMR signals (shifts) from Cu-Py complex have major contribution from Fermi contact interaction due to proximity of the organic arm to Cu2+ ion (Cu2+-C/H atoms 0-5 Å). The unpaired electron spin density distributed over the pyrazine-carboxylate organic arm is crucial in understanding Fermi contact shifts and hence accounts for 1H and 13C ssNMR signal assignment. The theoretical Fermi contact shifts together with diamagnetic shifts, calculated using density functional theory (DFT) at B3LYP level with basis sets viz. 6-311G, 6-311G+(D) and 6-311G++(D), were compared with the experimental shifts to facilitate the process of signal assignment. Vibrational analysis of Cu-Py complex was performed at B3LYP level of theory with various basis sets in comparison with experimental IR data. This further assisted in double validation of DFT optimized Cu-Py structure used here for extracting Fermi contact shifts. Furthermore molecular orbital analysis on the DFT optimized Cu-Py structure articulates the spin density distribution mechanism, thereby stipulating the location of the unpaired electron in the Cu(II) dx 2 -y 2 orbital in Paramagnetic Cu-Py complex.

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Polyaniline (PANI), a conducting polymer, has great interest for a large number of applications. However, poor processability and mechanical properties limits its usage and many methods like blending, grafting etc. are used to overcome this disadvantage. We have carried out grafting of PANI onto pullulan (PULL) via chemical oxidative polymerization technique. The percentage of grafting is favored by increasing concentration of aniline monomer. The formation of PANI is confirmed through UV–Vis spectroscopic studies. The possible grafting mechanism is studied using Fourier transform infrared spectroscopy and validated by Hartree‐Fock density functional theory (HF‐DFT) calculations. Further, thermal properties of grafted polymers are studied using differential scanning calorimetry and thermo gravimetric analysis. Using FESEM and x‐ray diffraction, structural properties of graft polymer were studied. DC electrical conductivity of grafted polymer is measured from I‐V characteristics, shows a significant conductivity which is the highlight of this work.

The synthesis method of lithiated d-metal oxides using molten formate mixtures as precursors has been developed and the isothermal (800°C) cross section of pseudo ternary Li-Mn-Co oxide system under ambient oxygen pressure has been investigated by XRD, 7 Li NMR, and galvanostatic electrochemical methods. Special attention has been paid to the compositions inside the quadrangle restricted by solid solutions LiCoO 2 -LiCo 0.85 Mn 0.15 O 2 with the layered structure of α-NaFeO 2 and solid solutions LiMn 2 O 4 -LiMnCoO 4 with the structure of spinel. It was found that, depending on the composition, three types of equilibrium phases could be formed: spinels Li[Li,Mn,Co] 2 O 4 with a part of Li atoms in octahedral sites, cation-deficit layered compounds Li 1 − δ [Co,Mn]O 2 , and Li 2 MnO 3 . Areas of (co)existence of these phases were plotted on the composition plane of the pseudo-ternary Li-Mn-Co system. Electrochemical properties of the compositions inside the quadrangle LiCoO 2 -LiCo 0.85 Mn 0.15 O 2 -LiMn 2 O 4 -LiMnCoO 4 are determined by the content and average oxidation number of Mn atoms, which is higher than in the normal spinels Li[Mn, Co] 2 O 4 . Thus, the specific capacities of the polyphase compositions are lower in comparison with the binary solid solutions Li[Mn,Co] 2 O 4 or pure LiCoO 2 .

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