Self-assembly patterns of non-metalloid silver thiolates: structural, HR-ESI-MS and stability studies.

Screening of AgNO3/AgStBu solutions in DMF, DMSO and NMP resulted in the isolation of three novel nanosized silver/thiolate complexes with a torus-like {Ag20(StBu)10} core. The structures of [NO3@Ag20(StBu)10(NO3)9(DMF)6] (1) and [NO3@Ag20(tBuS)10(NO3)8(NMP)8][NO3@Ag19(tBuS)10(NO3)8(NMP)6]2(NO3) (2) were studied by single crystal X-ray diffraction (SCXRD). The self-assembly process leading to 1 can be switched to a different outcome using Br-, resulting in [Br@Ag16(StBu)8(NO3)5(DMF)3](NO3)2 (3), which is the one of the few genuine host-guest complexes in the silver/thiolate systems. Solutions of the individual complexes in CH3CN were studied by HR-ESI-MS techniques, which revealed a dynamic behavior for each complex, driven by a redistribution of the {AgNO3} units. This dynamics results in the appearance of both cationic and anionic species, based on unchanged silver-thiolate cores. Daylight causes degradation of 3 with the formation of a composite material based on defective orthorhombic Ag2S with a porous morphology, as observed using the SEM technique. The electrocatalytic HER activity of such a material was studied.

Proton motion inside [(DMF)2H]2[W6Cl14]: structural, Raman and luminescence studies.

Protonation of DMF by (H7O3)2[W6Cl14] results in the appearance of strongly proton coupled [(DMF)2H]+ dimers. Such units are captured as the cationic part of [(DMF)2H]2[W6Cl14] (1). The proton behavior in such dimers was studied for the first time with single crystal X-ray diffraction (XRD) and 1H MAS NMR, Raman and photoluminescence (PL) spectroscopic techniques. The experimental data reveal the presence of two types of [(DMF)2H]+ dimers in 1 (cisoidal and transoidal, with respect to the mutual orientations of their C-O groups) which differ in terms of the degree to which they interact with the cluster anions as the temperature decreases. At room temperature all the OO distances in the [(DMF)2H]+ dimers are very short (2.375 Å) and almost equal. 1H MAS NMR spectra show a resonance line at 18.7 ppm which is very close to that observed in sodium hydrogen maleate with a strong hydrogen bond belonging to a single-well potential of proton motion. The temperature decrease leads to the differentiation of [(DMF)2H]+ dimers due to the elongation of the OO distance in one pair while keeping a practically constant OO distance in the second pair. The analysis of the cation-anion interactions reveals a strong difference between these two types of dimers which results from the shifting of one DMF molecule toward a terminal Cl- ligand of the cluster anion. The DFT calculations were used to show the difference in OH+O stretches for two different dimers. Moreover, we have found the PL of such dimeric units in the solid state. The temperature screening of the PL behavior demonstrates two types of luminescent centers at low temperatures which coalesce at 298 K. The proton motion in the hydrogen bond was studied using Raman spectroscopy, which was beneficial to monitor the complex behavior over a very broad temperature range from 5 to 298 K. According to the Raman data, we are dealing with a symmetric double-well potential for the hydrogen bond at room temperature, which becomes a broad single well potential below 110 K for the [(DMF)2H]+ cation with a longer OO distance (the cisoidal isomer) and below 60 K for the [(DMF)2H]+ cation with a shorter OO distance (the transoidal isomer).

[{AgL}2Mo8O26]n- complexes: a combined experimental and theoretical study.

Self-assembly reactions between AgNO3, L (PPh3, PPh2Py, AsPh3, SbPh3) and [ß-Mo8O26]4- in DMF led to the formation of [ß-{AgL}2Mo8O26]2- anions, which were isolated as Bu4N+ salts (1-4) and characterized by XRD, IR and elemental analysis. In the crystal structures Ag+ can switch the coordination number from 5 (P, As) to 6 (Sb) by uptake of a DMF molecule. High-level QAIM analysis of the coordination sphere around Ag shows critical points even in the case of longer Ag-O distances. Changing the ligand type to a family of substituted pyridines results in novel Ag-L-POM complexes with different environments around Ag+. For 3-X-pyridine ligands (X = Cl, Br, I), complexes with additional DMF molecules [ß-{AgL(DMF)}2Mo8O26]2- (5-7) have been isolated. Halogen bonding of the XO type was detected in the crystal structures of 5-7 and studied by DFT calculations, providing estimated energies from 0.9 to 3.4 kcal mol-1. Variation of substituents at the pyridine ring results in the formation of [ß-{AgL}2Mo8O26]2- in the case of 2-NH2-py (8), 2-CH3-Py (9), 2,4,6-collidine (10) and 2,6-NH2-py (11). Solution behavior of 1-4 in CH3CN was studied by a hyphenated HPLC-ICP-AES technique. According to the results, the [ß-{AgL}2Mo8O26]2- anions are largely dissociated in this medium. An attempt to change the [Mo8O26]4- precursor to [Mo6O19]2- (in the case of AgNO3 and PyPPh2) resulted in the crystallization of [Ag2(PyPPh2)2(DMF)4][Mo6O19] (12).