Experimental and Computational Studies on Aminoguanidine Free Base, Monocation and Dication, Part I: The Crystal and Molecular Structure of Aminoguanidine Monohydrochloride and the ab Initio Structure of the Endiamine Tautomer of Aminoguanidine Free Base

Abstract

The crystal and molecular structure of aminoguanidine monohydrochloride, CN4H 7+.CL, in which aminonoguanidine exists in the monocation form, was determined by single-crystal X-ray diffraction. The structure of the monocation is largely similar to that of aminoguani dine dication as present in previously studied divalent salts. The monocation was found to exist in the form of the tautom er that allows strong resonance in the guanyl group. As compared to the dication, the terminal hydrazine nitrogen atom bears one hydrogen atom less. The monocation is planar, the only atoms deviating from the plane being the hydrogens attached to the terminal hydrazine nitrogen. Q uantum chemical calculations on the endi amine tautomer of aminoguanidine free base as well as on aminoguanidine monocation and dication were also perform ed by using the HF and MP2 ab initio methods and also the B3-LYP and B-LYP methods based on density functional theory. On the basis of the calculations, a predicted structure of the endiamine tautom er of aminoguanidine free base is presented.

Platinum(II) and Palladium(II) Complexes with N‐Aminoguanidine

“…Distances and angles at the platinum centre have usual values, while distances and angles of the Amgu moiety are comparable to those observed for uncomplexed Amgu cations in the solid state. [16,[26][27][28] Distances C1-N1, C1-N2 and C1-N3 have approximately equal values, as should be expected for a delocalized guanidinium system. The Amgu ligand is approximately planar (maximum deviation from the least-squaresplane defined by the atoms C1, N1, N2, N3, and N4 is 0.039(2) Å for N3), confirming that nitrogen N3 is sp 2 hybridized.…”

“…Distances C1-N1, C1-N2 and C1-N3 are again of approximately equal values, and are comparable with those for protonated uncomplexed ligand. [16,[26][27][28] There is no localised double bond, and the positions of the H atoms and the planarity of the ligand suggest an sp 2 hybridisation for all atoms except N4, which remains sp 3 -hybridised. The packing of the Pt units gives rise to infinite stacks of square-planar complexes (correlated by a c glide plane) with a Pt-Pt separation of 3.332(1) Å.…”

Experimental and Computational Studies on Aminoguanidine Free Base, Monocation and Dication. Part III: Proton Affinities of Guanidine, Aminoguanidine and Glyoxal Bis(amidinohydrazone)

“…M o le cu les c o n ta in in g th e g ro u p s (N H 2)2-C = Na n d ( N H 2)2-C = N -N = h av e b e e n stu d ie d by b o th e x p e rim e n ta l [ 1 -8 ] a n d q u a n tu m chem ical m e th ods [4,9]. T h e sim p lest m o le cu les o f this k in d are g u a n id in e (N H 2) 2-C = N -H an d a m in o g u an id in e (N H 2)2-C = N -N H 2.…”

“…[1,32], g u a n id in e [16,24] and am in o g u an id in e [9] d e te rm in e d in a q u e o u s so lu tio n gives in fo rm a tio n o n th e d if fe re n t facto rs affectin g th e basicity o f th e se sp ecies in th e gas p h ase a n d in so lu tio n , respectively. [4], It is also k n o w n th a t especially B 3-L Y P e n e rg ies c a l c u la te d w ith la rg e r basis sets o n th e B 3 -L Y P /6 -3 1 G (d ) g e o m e trie s a re alm o st as a c c u ra te as M P2 en e rg ies [9,37], T h e re fo re , B 3 -L Y P /6 -3 1 G (d ) w as u sed fo r this study. F o r c o m p a riso n , th e c a lc u la tio n s w ere d o n e a t M P 2 /6 -3 1 G ( d ) an d M P 2 /6 -3 1 G (d ,p ) levels fo r g u an id in e a n d a m in o g u a n i dine, an d a t B 3 -L Y P /6 -3 1 G (d ,p ) fo r g u a n id in e a n d G B G .…”

Guanidylated hollow fiber membranes based on brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO) for gold sorption from acid solutions

“…After HAuCl 4 is added into the solution with GPPO HFM, AuCl 4 − anions may combine with the HFM by ion exchange or by coordination complexes. As the guanidyl group can transform into three resonance forms [28], there would be trivalence forms for electrostatic interactions and tetravalence forms for complexations (Fig. 9).…”