The layered crystal structure of piperazine-1,4-diium diiodide – diiodine (1:1), C4H12I4N2

C4H12I4N2, triclinic, P1 (no. 2), a = 6.4800(6) Å, b = 7.4090(7) Å, c = 8.0824(8) Å, ( = 63.939(10)°, ' = 67.290(10)°, ! = 69.471(9)°, V = 313.8 Å, Z = 1, Rgt(F) = 0.0201, wRref(F ) = 0.0507, T = 100 K. Source of material 86.1 mg (1 mmol) piperazine, 253.8 mg (1 mmol) I2 and 0.15 mL hydroiodic acid (58%; 2 mmol) were sealed in a thick-walled borosilicate glass tubing. Heating up to 130 °C and slow cooling (10 °C/h) to room temperature gave orange-red crystals of the title compound in almost quantitative yield. The Raman spectrum (Bruker MULTIRAM spectrometer (Nd:YAG-Laser at 1064 nm; RT-InGaAs-detector; back scattering geometry)) shows only one very strong signal at 169 cm whereas all other signals are weak. Experimental details The hydrogen atoms attached to the carbon atoms were included in the latest stages of the refinement using a riding model with their Uiso values set to 1.2Ueq(C). For the positions of the hydrogen atoms of the NH2 + group the AFIX 24 option of the SHELX system [2] was used which allows a change of the N–H distance during the refinement. One common Uiso value was refined for these two hydrogen atoms. The highest difference electron density peak (1.04 e! Å) is 0.88 Å apart from I1. Discussion Polyiodides, built from I, I2 and I3 – subunits, fulfill the general formula I m n n 2 $ " (n = 1–4, m = integer) [4–8] and are connected via halogen bonds. The halogen bonding received much attention because of its influence on the functionality of biological systems and its role in the crystal engineering of new materials for various applications [9, 10]. Because of their potential use as Agent Defeat Weapons (ADW) [11] there is a general interest in iodinerich compounds. Furthermore, it has been proved that diaminium and pyridinium iodides and corresponding polyiodides influence the redox chemistry in dye-sensitized solar cells [12, 13]. Several new polyiodides have been synthesized and structurally characterized in the (,)-diamonioalkane iodide / diiodine system [14–18]. In these cases the lengths of the stick-shaped cations excellently fit with the topologies of the corresponding polyiodides. This synthetic protocol is known as dimensional caging [19]. This contribution is part of our ongoing interest on the synthesis of new polyiodides using nitrogen containing cyclic cations [20–22]. The asymmetric unit of the title structure contains one half of a piperazine-1,4-diium dication (pipH2 ) and one half of a diiodine molecule, both located around inversion centers. Whereas the iodide anion is placed in a general position. The geometric parameters of the pipH2 2+ cation exhibiting an all-chair conformation are all in the expected ranges (C–C: 1.505(7) Å; C–N: 1.485(6) and 1.498(6) Å). All moieties are connected by hydrogen and halogen bonds, respectively (Figure, upper part; ' = 1–x, 1–y, 1–z; '' = 2–x, –y, –z) [23]. Each dication is connected to four iodide anZ. Kristallogr. NCS 229 (2014) 423-424 / DOI 10.1515/ncrs-2014-9031 423 © 2014 by Walter de Gruyter Berlin/Boston Crystal: orange-red blocks, size 0.163$0.305$0.5395 mm Wavelength: Mo K" radiation (0.71073 Å) &: 98.83 cm Diffractometer, scan mode: Xcalibur, Eos, ) 2%max: 50.95° N(hkl)measured, N(hkl)unique: 4047, 1157 Criterion for Iobs, N(hkl)gt: Iobs > 2 #(Iobs), 1127 N(param)refined: 49 Programs: CrysalisPRO, SHELX, DIAMOND [1–3] Table 1. Data collection and handling.