Crystal and Species Engineering with Semi‐Flexible Nitrogen Containing Organic Cations: Generation of [H₁₃O₆]⁺Ions with the Unfavoured Unbranched Topology by Enclosing Hydrochloric Acid in a Porous Inorganic‐Organic Hybrid Material

Abstract

The reaction of rhodium(III) chloride trihydrate with 1, 4‐diazacycloheptane in concentrated hydrochloric acid results in the formation of tris(1, 4‐diazoniacycloheptane) hexaaquahydrogen(1+) bis(hexachlororhodate(III)) chloride, [C5H14N2]3[H13O6][RhCl6]2Cl (1). Dark red crystals of 1 are obtained by diffusion‐controlled crystallization at room temperature. Slow evaporation of the mother liquor over a period of several days yields a few tiny crystals of the bis(1, 4‐diazoniacycloheptane) hexachlororhodate(III) chloride hydrate, [C5H14N2]2[RhCl6]Cl˙1.75 H2O (2), as red thin squared plates. In the context of crystal engineering, compounds 1 and 2 are inorganic‐organic hybrid materials built up from octahedral [RhCl6]3‐, simple Cl‐ and semi‐flexible heterocyclic 1, 4‐diazoniacycloheptane ions, incorporating either the [H13O6]+ and further Cl‐ ions or portions of simple water molecules. Both compounds crystallize in the space group type P21/c. Compound 1 contains isolated [H13O6]+ ions with a linear chain‐like configuration enclosed in the cavities of the inorganic‐organic framework. The presence of a strong central O···H···O hydrogen bond within the [H13O6]+ ions in 1 is confirmed by the short O···O separation of 2.47Å and by characteristic IR absorption bands at 1626 (s), ∼ 1250 (m) and 668 (m) cm‐1. During the thermal decomposition, compound 1 looses at first five equivalents of water and one equivalent of hydrochloric acid in a two‐step process at 37 °C and 67 °C. This is followed by the decomposition of the 1, 4‐diazoniacycloheptane cations and the hexachlororhodate(III) anions, starting at 190 °C and proceeding intensified at 240 °C.

Efficient Diffusion-Controlled Ligand Exchange Crystal Growth of Isostructural Inorganic–Organic Halogenidorhodates(III): The Missing Hexaiodidorhodate(III) Anion

“…This suggests that they are stable at ambient conditions over long time scales, in contrast to the other compounds of this class. 23 Further, compound 1 was found to easily and repeatedly crystallize at different experimental conditions involving different (i) molar ratios of starting materials (piperazine to rhodium(III) chloride trihydrate molar ratios of 1:10, 6:1, and 10:1), (ii) concentrations of hydrobromic acid (ca. 9, 4.5, and 3 mol/L HBr for the same 6:1 molar ratio of starting materials), and (iii) method/temperature of crystallization−hydrothermal 24 and diffusion-controlled 8,11 processes (for the substrates molar ratio of 2:1).…”

The Triple Salt 2(C7H9N4O2)[MoOCl4(H2O)] ⋅ 2(C7H9N4O2)Cl ⋅ (H17O8)Cl Containing a C2‐symmetrical Unbranched H+(H2O)8Zundel type Species in a Framework Composed of Theophyllinium, Aquatetrachloridooxidomolybdate and Chloride Ions

“…However, 3D and 2D structural isomers, only, have been identified as minima of the energy hypersurfaces at B3LYP/aVDZ, MP2/CBS or CCSD(T)/CBS levels of theory [23] . The example most closely related to the hydrated proton species in 1 , seems to be the unbranched H 13 O 6 + ion found in the inorganic‐organic hybrid solid tris(1,4‐diazoniacycloheptane) hexaaquahydrogen(1+) bis(hexachloridorhodate(III)) chloride, [C 5 H 14 N 2 ] 3 [H 13 O 6 ][RhCl 6 ] 2 Cl ( 2 ) [11] . With crystallographic inversion symmetry imposed it is characterized by a strong central hydrogen bond with an O⋅⋅⋅O separation of 246.9 pm.…”

“…The O⋅⋅⋅O distances as an indirect measure of the strength of hydrogen bonding allow for an identification of H + (H2O) n species in literature that are not explicitly addressed in the corresponding publications via crystallographic data bases. However, up to now, to the best of our knowledge, only three solid state structures can be identified comprising a chain‐like H + (H 2 O) n cationic moiety with n >4 as a distinct structural unit (n=5, [17e] n=6 [11,17g] ), which is not connected by further O⋅⋅⋅H⋅⋅⋅O hydrogen bonds as for example in the one‐ and two‐dimensional polymeric (H 13 O 6 + ) n units in (H 13 O 6 )Cl [20] and (H 13 O 6 )[FeCl 4 ], [21] respectively.…”

“…However, 3D and 2D structural isomers, only, have been identified as minima of the energy hypersurfaces at B3LYP/aVDZ, MP2/CBS or CCSD(T)/CBS levels of theory. [23] The example most closely related to the hydrated proton species in 1, seems to be the unbranched H 13 [11] With crystallographic inversion symmetry imposed it is characterized by a strong central hydrogen bond with an O•••O separation of 246.9 pm. However, taking a closer look at the central H 5 O 2 + species of this ion, the bonding situation as compared to 1 is different in two important aspects, i) the site symmetry of the proton's (H 2 O) 2 environment is � 1 and not 2, and ii) the O•••O distance is definitely beyond the limit of the region that is supposed to be indicative for very strong OÀ HÀ O hydrogen bonds (< 245 pm).…”

Crystal structure of 1,10-phenanthrolindiium bis(triiodide) monohydrate, C12H12I6N2O

“…Those two commoninteractions are used to create new systems that develop our understanding of molecular and ionic behavior in the various solid-state environments [1,2].Recently, we have developed the concept of the halogenido-ligand exchange synthesis for inorganic-organic halogenidorhodate(III) materials [3,4].Tobetter understand structure and properties of those hybrid systemswe have determined the structure of somes imple salts of nitrogen containing basesl ike1 ,10-phenanthrolindiium bis(triiodide) monohydrate comprising one of the most important organic ligands of many metal complexes and hybrids, the 1,10-phenanthrolindiium cation [5,6] 2+ cations are essentially planar with no atom deviatingfromthe least-squaresplanesbymore than 0.075(4) Å. Their N-C and C-C distances and bond angles are in the expected ranges and are similar to those in previously reported structures [7][8][9].Both triiodide anions are not strictly linear with the angles I1-I2-I3 and I4-I5-I6 of 174.891 (12) 0.0321(6) and 0.0091(6) Åinthe I-I distances within I 3 -ions are relatively small, they are statistically significant.…”