Three-dimensional organic-inorganic hybrid sodium halide perovskite: C4H12N2·NaI3 and a hydrogen-bonded supramolecular three-dimensional network in 3C4H12N2·NaI4·3I·H2O.

The rational selection of ligands is vitally important in the construction of new organic-inorganic hybrid three-dimensional perovskite complexes. As part of an exploration of perovskite-type materials, two new Na-I compounds based on the piperazine ligand, namely poly[piperazinediium [tri-μ-iodido-sodium]], {(C4H12N2)[NaI3]}n, 1, and catena-poly[tris(piperazinediium) [[triiodidosodium]-μ-iodido] triiodide monohydrate], {(C4H12N2)3[NaI4]I3·H2O}n, 2, have been synthesized by adjusting the stoichiometric ratio of sodium iodide and piperazine, and were characterized by single-crystal X-ray diffraction. In the crystal structures of 1 and 2, each NaI cation is linked to six I atoms, but the compounds show completely different configurations. In 1, the structure includes a perovskite-like array of vertex-sharing NaI6 octahedra stretching along the direction of the three axes, and each piperazinediium dication is enclosed in the NaI3 perovskite cage. However, in 2, each NaI atom bridges a single I atom to form a one-dimensional linear chain, and complex intermolecular hydrogen bonds connect these one-dimensional chains into a three-dimensional supramolecular network. open access.

Introduction

In recent decades, three-dn class="Chemical">imensional organic–inorganic hybrid perovskites have been of inter­est to researchers, not only for their remarkable structural variability and highly tunable properties, but also for their rich physical properties, such as superconductivity, ionic conductivity and ferroelectric related properties (Jin et al., 2009 ▸; Saparov & Mitzi, 2016 ▸; Veldhuis et al., 2016 ▸). Such hybrid perovskites have a simple generic formula of AMX 3 (A = organic cation, M = metal cation and X = halogen anion) and the structural characteristic of corner-sharing MX 6 octa­hedra. Among them, there have been a large number of reports on the halometallates of PbII and SnII ions because of their superior semiconducting properties, but related systems containing alkali metal halides are rare (Lee et al., 2003 ▸; Shi et al., 2017 ▸; Liao et al., 2016b ▸; Galkowski et al., 2016 ▸; Yang et al., 2015 ▸; Liao et al., 2016a ▸). To be precise, the first alkali metal halide perovskites, RMCl3 (R = piperazine and M = K, Rb and Cs), were found less than ten years ago (Paton & Harrison, 2010 ▸). In recent years, due to the development of mol­ecular ferroelectric materials (You et al., 2017 ▸; Xu et al., 2017 ▸; Liao et al., 2017 ▸), three-dimensional alkali metal halide perovskites have attracted the attention of researchers again. Just last year, Xiong and co-workers reported two high-T c three-dimensional perovskite ferroelectric materials, i.e. [3-ammonio­pyr­roli­dinium]·RbBr3 and [N-methyl-1,4-diazo­niabi­cyclo­[2.2.2]octa­ne]·RbI3 (Pan et al., 2017 ▸; Zhang et al., 2017 ▸).

Following on from thn class="Chemical">is work, we report the new three-dimensional organic–inorganic hybrid perovskite C4H12N2·NaI3 (1). In addition, considering that the dimensionality of three-dimensional perovskites can often be switched by alteration of the experimental conditions (e.g. CH3NH3·PbI3; Jodlowski et al., 2016 ▸), we obtained a new compound, i.e. 3C4H12N2·NaI4·3I·H2O (2) with a peculiar one-dimensional [NaI5]4− linear chain and a three-dimensional hydrogen-bonded supra­molecular network by adjusting the stoichiometry of piperazine and sodium iodide.

Experimental

Synthesis and crystallization

Synthesis of C4H12N2·NaI3, (1)

An aqueous solution (20 ml) of n class="Chemical">sodium iodide (1.49 g, 10 mmol) was added dropwise to an equimolar ratio of piperazine (0.86 g, 10 mmol) in water (5 ml) with stirring. The solution was then filtered to remove insoluble impurities. Yellow block-shaped crystals of 1 suitable for X-ray diffraction were obtained by slow volatilization of the aqueous solution at 330 K after 2 d.

Synthesis of 3C4H12N2·NaI4·3I·H2O, (2)

An aqueous solution (20 ml) of n class="Chemical">sodium iodide (0.75 g, 5 mmol) was added dropwise to an aqueous solution (5 ml) of piperazine (1.29 g, 15 mmol). The solution was stirred for 20 min and then filtered to remove insoluble impurities. Yellow needle-shaped crystals of 2 were obtained by slow volatilization of the aqueous solution at 330 K after 2 d.

Refinement

Crystal data, data collection and structure refn class="Chemical">inement details are summarized in Table 1 ▸. H atoms bonded to O atoms were located from difference Fourier maps and refined with an O—H distance restraint of 0.85 (1) Å. Other H atoms were placed in idealized positions and included as riding, with C—H = 0.97 Å (methyl­ene) or N—H = 0.89 Å. U iso(H) values were set at 1.2U eq(C,N) for methyl­ene and piperazinediium, and at 1.5U eq(O) of water H atoms.

Table 1

Experimental details

	1	2
Crystal data
Chemical formula	(C4H12N2)[NaI3]	(C4H12N2)3[NaI4]I3·H2O
M r	491.85	1193.77
Crystal system, space group	Monoclinic, C2/c	Monoclinic, P21/n
Temperature (K)	293	293
a, b, c (Å)	9.842 (6), 9.309 (6), 12.538 (8)	12.186 (2), 22.828 (5), 12.214 (2)
β (°)	93.450 (9)	111.89 (3)
V (Å3)	1146.6 (13)	3152.7 (12)
Z	4	4
Radiation type	Mo Kα	Mo Kα
μ (mm−1)	8.16	6.92
Crystal size (mm)	0.38 × 0.28 × 0.20	0.38 × 0.28 × 0.20
Data collection
Diffractometer	Rigaku SCXmini
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2008 ▸)
T min, T max	0.080, 0.195	0.112, 0.251
No. of measured, independent and observed [I > 2σ(I)] reflections	3288, 1311, 1153	20677, 7234, 4432
R int	0.083	0.075
(sin θ/λ)max (Å−1)	0.648	0.649
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.058, 0.165, 1.03	0.085, 0.142, 1.09
No. of reflections	1311	7234
No. of parameters	48	252
No. of restraints	0	2
H-atom treatment	H-atom parameters constrained	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	1.80, −1.66	1.23, −1.05

Computer programs: CrystalClear (Rigaku, 2008 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and DIAMOND (Brandenburg & Putz, 2005 ▸).

Results and discussion

Structure of C4H12N2·NaI3, (1)

Compound 1 crystallizes n class="Chemical">in the monoclinic system (space group C2/c) and exhibits the three-dimensional perovskite framework. The asymmetry unit (Fig. 1 ▸) includes one NaI cation located on a twofold axis, one half of a piperazinediium dication located about a centre of inversion and two iodide ions attached to the NaI cation. As shown in Fig. 2 ▸, 1 is different from C4H12N2·KCl3·H2O, due to the Na—I bond length being less than that of K—Cl (Table 2 ▸); the NaI6 perovskite cage encloses one piperazinediium cation and prevents the entry of water mol­ecules. In addition, the H atoms on the C and N atoms of piperazinediium form weak hydrogen bonds with the I atoms in the cage, resulting in significant octa­hedral tilting (Fig. 3 ▸). According to Glazer’s 23 tilt system (Glazer, 1972 ▸, 1975 ▸), the octa­hedral tilting of compound 1 should belong to the ‘a−b−b−’ type. Detailed information of the C—H⋯I and N—H⋯I hydrogen bonds is given in Table 3 ▸. It can be seen from the packing diagram (Fig. 4 ▸) that the piperazinediium cations in the ab plane are arranged along the same direction; however, the piperazinediium cations along the c axis are arranged in a zigzag manner, viz. ‘\/\’. In summary, compound 1 has the familiar three-dimensional perovskite framework structure, where the piperazinediium cations are confined in the cavities enclosed by corner-sharing NaI6 octa­hedra and stabilized by C—H⋯I and N—H⋯I hydrogen bonds.

Figure 1

A view of the asymmetric unit in compound 1. All H atoms have been omitted for clarity. [Symmetry codes: (i) −x + 1, −y + 2, −z + 1; (ii) x − , y + , z; (iii) −x + 1, −y + 1, −z + 1; (iv) −x + 1, y, −z + ; (v) x + , y − , z; (vi) −x + , y − , −z + .]

Figure 2

(a) A view of the three-dimensional perovskite cage of C4H12N2·KCl3·H2O. (b) A view of the three-dimensional perovskite cage of compound 1.

Table 2

Selected geometric parameters (Å, °) for 1

C2—C1	1.504 (14)	Na1—I2	3.156 (2)
C2—N1i	1.532 (14)	Na1—I1	3.325 (5)
N1—C1	1.456 (13)
Na1—I1—Na1ii	169.12 (12)	I2—Na1—I1v	84.40 (9)
Na1iii—I2—Na1	180.0	I2iv—Na1—I1vi	84.40 (9)
N1—C1—C2	111.6 (8)	I1vi—Na1—I1v	100.45 (19)
I2iv—Na1—I1	101.40 (10)	I1—Na1—I1v	169.12 (12)
I2—Na1—I1iv	101.40 (10)	I1iv—Na1—I1vi	169.12 (12)
I2iv—Na1—I2	166.6 (3)	I1iv—Na1—I1	86.15 (18)
I2—Na1—I1	88.41 (8)	I1iv—Na1—I1v	87.29 (5)
I2iv—Na1—I1iv	88.41 (8)	I1—Na1—I1vi	87.29 (5)
I2iv—Na1—I1v	87.06 (9)	C1—C2—N1i	108.4 (9)
I2—Na1—I1vi	87.06 (9)	C1—N1—C2i	110.2 (8)

Symmetry codes: (i) ; (ii) ; (iii) , ; (iv) ; (v) ; (vi) .

Figure 3

The hydrogen bonds (dashed lines) in 1 of the C and N atoms of the piperazinediium cation with the I atoms of the NaI6 octa­hedra. [Symmetry codes: (i) −x + 1, −y + 2, −z + 1; (ii) x − , y + , z; (iv) −x + 1, y, −z + ; (vii) −x + , −y + , −z + 1; (viii) x + , −y + , z + .]

Table 3

Hydrogen-bond geometry (Å, °) for 1

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1D⋯I1i	0.97	3.12	3.937 (11)	143
C1—H1C⋯I2	0.97	3.23	3.914 (11)	129
C1—H1C⋯I1vii	0.97	3.14	3.790 (10)	126
C2—H2B⋯I1viii	0.97	3.17	3.930 (11)	136
C2—H2A⋯I1iv	0.97	3.23	3.930 (13)	131
N1—H1B⋯I1i	0.89	2.80	3.628 (10)	156
N1—H1A⋯I2ii	0.89	3.11	3.677 (8)	123
N1—H1A⋯I1vii	0.89	3.14	3.746 (8)	127

Symmetry codes: (i) ; (ii) ; (iv) ; (vii) ; (viii) .

Figure 4

A packing view of compound 1, showing the three-dimensional perovskite structure.

Structure of 3C4H12N2·NaI4·3I·H2O, (2)

Compound 2 crystallizes n class="Chemical">in the monoclinic system (space group P21/n) but displays a one-dimensional linear chain-like geometry. The asymmetry unit contains three whole piperazinediium cations, one lattice water mol­ecule, two dissociated iodide ions and one Na atom in a glide plane coordinated with five iodide ions. As can be seen from Fig. 5 ▸, each Na atom is coordinated by six I atoms, and two Na atoms are bridged by one I atom and extended in an infinite manner along a horizontal direction, thus presenting a one-dimensional linear chain. As shown in Table 4 ▸, the length of the Na—I bonds are within the reasonable range 3.180 (5)–3.515 (6) Å and the I—Na—I angles are in the ranges 84.32 (14)–94.56 (16) and 176.97 (18)–178.20 (17)°. It is worth noting that there are very complex hydrogen bonds in compound 2. These hydrogen bonds can be divided roughly into four types (Fig. 6 ▸): (i) piperazinediium N atoms act as donors and water O atoms act as acceptors in N—H⋯O hydrogen bonds (red dashed lines); (ii) water O atoms act as donors and I atoms in the metal halide chain act as acceptors in O—H⋯I hydrogen bonds (green dashed lines); (iii) piperazinediium N atoms act as donors and bridging I atoms act as acceptors in N—H⋯I hydrogen bonds (yellow dashed lines); (iv) piperazinediium N atoms act as donors and the free I atoms act as acceptors in N—H⋯I hydrogen bonds (blue dashed lines). Detailed information of the hydrogen bonds is given in Table 5 ▸. As shown in Fig. 7 ▸, the water H atoms form hydrogen bonds with the I atoms on the two sides of the NaI5 chain (i.e. O1i—H1⋯I5ii and O1i—H2⋯I2ix; Table 5 ▸), thus forming a two-dimensional network on the ac plane. On the other hand, the free I atoms (i.e. I6 and I7) and the bridging I atoms (i.e. I3) form N—H⋯I hydrogen bonds with the H atoms of the piperazinediium N atoms, which extends the two-dimensional network into a three-dimensional hydrogen-bonded supra­molecular network (Fig. 8 ▸).

Figure 5

A view of the asymmetric unit in compound 2. All H atoms have been omitted for clarity. [Symmetry codes: (i) x − , −y + , z − ; (ii) x + , −y + , z + .]

Table 4

Selected geometric parameters (Å, °) for 2

C1—N1	1.515 (14)	C9—C10	1.480 (18)
C1—C2	1.511 (18)	C10—N6	1.477 (13)
C2—N2	1.451 (16)	C11—C12	1.514 (17)
C3—N1	1.481 (14)	C11—N5	1.487 (13)
C3—C4	1.519 (16)	C12—N6	1.509 (13)
C4—N2	1.447 (17)	I1—Na1	3.419 (6)
C5—C6	1.527 (16)	I2—Na1	3.205 (5)
C5—N3	1.472 (13)	I3—Na1	3.381 (5)
C6—N4	1.452 (14)	I3—Na1i	3.456 (5)
C7—C8	1.532 (16)	I4—Na1	3.515 (6)
C7—N3	1.475 (13)	I5—Na1	3.180 (5)
C8—N4	1.486 (14)	Na1—I3ii	3.456 (5)
C9—N5	1.493 (14)
C10—N6—C12	111.1 (9)	I3—Na1—I1	91.38 (13)
C10—C9—N5	110.8 (10)	I5—Na1—I4	94.12 (14)
C11—N5—C9	110.5 (8)	I5—Na1—I3ii	92.63 (13)
C2—C1—N1	111.0 (10)	I5—Na1—I1	86.95 (13)
C3—N1—C1	109.5 (10)	I5—Na1—I3	88.73 (12)
C4—N2—C2	114.6 (12)	I5—Na1—I2	177.4 (2)
C5—N3—C7	112.7 (10)	N1—C3—C4	113.1 (10)
C6—N4—C8	111.8 (10)	N2—C4—C3	109.0 (11)
I1—Na1—I4	178.20 (17)	N2—C2—C1	108.3 (11)
I1—Na1—I3ii	91.40 (13)	N3—C7—C8	110.8 (10)
I2—Na1—I4	84.32 (12)	N3—C5—C6	110.7 (10)
I2—Na1—I3ii	89.46 (12)	N4—C8—C7	105.3 (11)
I2—Na1—I1	94.56 (14)	N4—C6—C5	106.4 (10)
I2—Na1—I3	89.12 (13)	N5—C11—C12	111.3 (10)
I3ii—Na1—I4	90.00 (12)	N6—C12—C11	109.0 (10)
I3—Na1—I4	87.19 (13)	N6—C10—C9	110.8 (10)
I3—Na1—I3ii	176.97 (18)	Na1—I3—Na1i	176.87 (7)

Symmetry codes: (i) ; (ii) .

Figure 6

A partial view of the crystal packing of compound 2, showing the inter­molecular N—H⋯I (blee and yellow dashed lines), N—H⋯O (red dashed lines) and O—H⋯I (green dashed lines) hydrogen bonds. All H atoms on C atoms have been omitted for clarity. [Symmetry codes: (i) x − 2, y, z; (ii) −x − , y + , −z + ; (iii) −x, −y + 2, −z + 1; (iv) −x − 1, −y + 1, −z + 1; (v) x − , −y + , −z + ; (vi) x − 2, y + 1, z; (vii) −x − , y + , −z + ; (viii) x − , −y + , z − ; (ix) −x − 1, −y + 1, −z + 1; (x) −x − , y + , −z + ; (xi) x − , −y + , z − ; (xii) x − 2, y + 1, z; (xiii) x − , −y + , z + .]

Table 5

Hydrogen-bond geometry (Å, °) for 2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N6vi—H6B⋯I6vi	0.89	2.99	3.626 (11)	130
N6vi—H6A⋯O1iii	0.89	1.97	2.856 (16)	175
N5vi—H5B⋯O1ii	0.89	1.99	2.878 (15)	178
N5vi—H5A⋯I7xii	0.89	2.83	3.557 (10)	140
N4v—H4B⋯I6xiii	0.89	2.55	3.440 (12)	175
N4v—H4A⋯I5vii	0.89	2.99	3.663 (13)	134
N4v—H4A⋯I1vii	0.89	3.25	3.881 (14)	130
N3v—H3B⋯I4iv	0.89	3.22	3.748 (11)	121
N3v—H3B⋯I3ix	0.89	3.22	3.767 (12)	122
N3v—H3B⋯I2ix	0.89	3.04	3.610 (11)	124
N3v—H3A⋯I7xii	0.89	2.68	3.543 (12)	165
N2iv—H2B⋯I2ix	0.89	3.14	3.867 (16)	140
N2iv—H2A⋯I3ix	0.89	2.70	3.405 (13)	138
N1iv—H1B⋯I6xi	0.89	2.62	3.496 (11)	169
N1iv—H1A⋯I7xii	0.89	2.92	3.613 (11)	136
N1iv—H1A⋯I1viii	0.89	3.32	3.804 (11)	117
O1i—H2⋯I2ix	0.85 (1)	2.68 (9)	3.471 (12)	155 (18)
O1i—H1⋯I5ii	0.85 (1)	2.69 (4)	3.501 (11)	161 (11)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) , ; (viii) ; (ix) ; (x) , ; (xi) ; (xii) ; (xiii) .

Figure 7

The hydrogen bonds of the O—H⋯I (green dashed lines) and N—H⋯O (red dashed lines) types in 2, showing the two-dimensional network on the ac plane.

Figure 8

A packing view of compound 2, showing the three-dimensional hydrogen-bonded network.

Summary

Two new organic–n class="Chemical">inorganic hybrid sodium halides have been synthesized by adjusting the stoichiometric ratio of sodium iodide and piperazine. C4H12N2·NaI3, 1, presents an inter­esting three-dimensional perovskite structure. However, compound 3C4H12N2·NaI4·3I·H2O, 2, features a singular three-dimensional hydrogen-bonded network. The different structures of compounds 1 and 2 show that the stoichiometric ratio plays a key role in the synthesis of various frameworks.

Crystal structure: contains datablock(s) C2C, C, global. DOn class="Chemical">I: 10.1107/S2053229618006885/qp3008sup1.cif

Structure factors: contains datablock(s) C2C. DOn class="Chemical">I: 10.1107/S2053229618006885/qp3008C2Csup2.hkl

Structure factors: contains datablock(s) C. DOn class="Chemical">I: 10.1107/S2053229618006885/qp3008Csup3.hkl

CCDC references: 1826738, 1826739