Structure determination of novel ionic co-crystals from powder data: the use of rigid fragments in simulated annealing algorithms

Abstract

A new approach is presented here for the structural solution of anhydrous and hydrated metal-organic coordination compounds of alkali and alkaline earth metals by using rigid structure fragments in combination with simulated annealing algorithms. We empirically show how this approach minimizes computation time, while allowing us to obtain the correct result. The structures of two novel ionic cocrystals have been solved from powder data with this approach.

Crystal structures of [Cu2(2,2′-bipyridine-N,N′)2(H2O)2(μ2-OH)2](barbiturate)2·2H2O and [Cu(2,2′-bipyridine-N,N′)(H2O)(barbiturate-O)Cl]·2H2O

“…As in the main bond lengths and valence angles of Hbaand Bipy in 2 practically coincide with those found earlier in other related compounds [13]. All the C-O distances in 1 and 2(Table 2S)are larger than those in free H 2 ba[32], indicating the charge delocalization in the Hbaion, as in the case of other barbiturate complexes[2][3][4][5][6][7][8][9][10][11][12]. The higher d(O3B-C6B ) = 1.2834 (17) Å value as compared with the smaller d(O1B-C2B ) = 1.2393 (18) Å and d(O2B-C4B ) = 1.2567(19) Å values can be explained by the coordination of the ligand Hba  to copper(II) via an O3B atom.…”

“…However, the crystal structure of the barbiturate complexes with metal ions has been the subject of only few reports [2][3][4][5][6][7][8][9][10][11][12]. Another well-known ligand in supramolecular chemistry is 2,2'bipyridine (Bipy).…”

Two salts and the salt cocrystal of ciprofloxacin with thiobarbituric and barbituric acids: The structure and properties

“…For example, d(O–C) of H 2 ba in salt cocrystals Rb(Hba)(H 2 ba)·3H 2 O, M(Hba)(H 2 ba)·3H 2 O (M=Na, K), K(Hba)(H 2 ba) 0.5 ·1.5H 2 O, MBr·H 2 ba (M=Na, K, Rb, Cs), and CsI·H 2 ba are in the range of 1.21 to 1.22 Å, but these values of Hba − are bigger, and they are in the range of 1.23 to 1.27 Å as in other compounds . The distances O–C in the trioxo form of detached H 2 ba (1.21‐1.22 Å) are similar to those in the above mentioned cocrystals and compounds [Ca(μ 3 ‐H 2 ba–O,O′,O″)]X 2 (X=Cl and I). The C–O distances d(O–C2) = 1.209 Å, d(O2–C4) = 1.269 Å, and d(HO–C6) = 1.332) Å in the H 2 ba enol form show that the protonation of one of the O atoms increases the corresponding bond …”

Calcium and strontium thiobarbiturates with discrete and polymeric structures

“…[23][24][25], and C, with variation in the type metal [12]. Unlike the d-elements, the alkali metals (Na, K, Rb, Cs) [26] and Ca 2+ cations [27] connect only through the carbonyl O. However, in [Ba 2 H(Barb) 5 ] (Barb − = 5,5-diethyl barbiturate anion), Ba 2+ is bound to the ligand through both O and N [28].…”