Synthesis and X-ray structural studies of pentaborate(1−) salts containing substituted imidazolium cations

Abstract

The preparation of [NMC][B5O6(OH)4] {NMC = 2-MeC3N2H4 (3),1-MeC3N2H4 (4), 4-MeC3N2H4 (5), 1,2-Me2C3N2H3 (6), 1,2,3-Me3C3N2H2 (7), 1-EtC3N2H4 (8), 2-EtC3N2H4 (9), 2-Et-4-MeC3N2H3 (10) 1-Et-3-MeC3N2H3 (11) and 2-i PrC3N2H4 (12)} salts are reported. Compounds were characterized by spectroscopy (NMR and IR) and by single crystal XRD (6, 7, 9, 10, 12) studies. All structures show extensive H-bonded networks and 7 displays the first example of reciprocal paired  anion-anion interactions.These are facilitated by the pentaborate boroxole rings being significantly distorted

Synthesis, XRD Studies and NLO Properties of [p-H2NC6H4CH2NH3][B5O6(OH)4]·1/2H2O and NLO Properties of Some Related Pentaborate(1−) Salts

“…At higher temperatures (200-800°C) oxidation of the organic cation occurs (exothermic) and this results in the formation of a boron oxide residue. These observations are consistent with the decomposition of other nonmetal pentaborate(1-) compounds in air [10][11][12][13] and under an inert (Ar/N 2 ) atmosphere [1,2,32,33].…”

“…This is not the case for 1 where the water molecules link between pentaborate(1-) anions and form part of the giant network (rather than as a cavity filler) resulting in a unique structure. Bond lengths and bond angles within the boroxole rings of the pentaborates are within ranges commonly seen in other pentaborate(1-) salts [4,5,[7][8][9][10][11][12][13][24][25][26] and in related boroxole containing systems [27][28][29]. Some summary data are given in the legend to Fig.…”

“…Inspection of XRD data of a number of other non-metal cation pentaborate salts which had previously been synthesized in our laboratories revealed that some of them also crystallized in non-centrosymmetric points groups. These compounds [11][12][13] were re-synthesized and their SHG efficiencies were also determined. 4 ] [19] and obtained a SHG efficiency of 0.6.…”

“…We have prepared a number of [NMC][B 5 O 6 (OH) 4 ] salts by the former method [7][8][9][10][11][12]. The principal aim of our studies was to investigate the role of the cation in these templating reactions using structural (XRD) and computational (DFT) methods [13,14].…”

“…This manuscript describes the synthesis and characterization 1, including it solid-state structure, and an investigation into its thermal and NLO (SHG) properties. A review of the structures of non-metal cation pentaborates that we had previously prepared [11][12][13] prompted us to re-synthesize those with non-centrosymmetric point groups in order to examine their NLO properties. This manuscript also reports on these results.…”