New Low-Dimensional Hybrid Perovskitoids Based on Lead Bromide with Organic Cations from Charge-Transfer Complexes

: We have obtained a series of low-dimensional hybrid perovskitoids (often referred to as perovskites) based on lead bromide. As organic cations, the derivatives of polyaromatic and conjugated molecules, such as anthracene, pyrene and (E)-stilbene, were chosen to form charge-transfer complexes with various organic acceptors for use as highly tunable components of hybrid perovskite solar cells. X-ray diffraction analysis showed these crystalline materials to be new 1D-and pseudo-layered 0D-perovskitoids with lead bromide octahedra featuring different sharing modes, such as in unusual mini-rods of four face- and edge-shared octahedra. Thanks to the low dimensionality, they can be of use in another type of optoelectronic device, photodetectors.


Introduction
Solar cells made with hybrid perovskite semiconductors [1] are believed to have a potential to revolutionize the field of renewable energy sources. These crystalline materials of the general formula AMX 3 feature a three-dimensional periodic array of corner-sharing MX 6 octahedra, where M is a large divalent metal ion (most often, Pb 2+ ) and X is a halide anion (I − , Br − or Cl − ), with voids filled by organic cations A, such as methylammonium or formamidinium. Owing to an ability to produce high-quality single crystals and films with tunable optoelectronic characteristics [2], the hybrid perovskites are superior to crystalline silicon, a popular component of solar cells. They, however, suffer from low stability [3] and soon degrade when exposed to oxygen, moisture, heat and even sunlight.
In this work, we synthesized a series of hydrobromides from previously reported [29][30][31][32] methanamine derivatives of anthracene, pyrene and (E)-stilbene, the popular donors In this work, we synthesized a series of hydrobromides from previously reported [29][30][31][32] methanamine derivatives of anthracene, pyrene and (E)-stilbene, the popular donors from charge-transfer complexes [26]. The corresponding cations (Scheme 1) have an alkylammonium group to bind the inorganic component of a hybrid perovskite via strong hydrogen bonds and a polyaromatic or conjugated core, to form a charge-transfer complex with an organic acceptor [26,27], such as tetracyanoethylene (TCNE). Their subsequent reaction with lead bromide in dimethylformamide, which provides a good solubility of both organic and inorganic compounds of our choice [21,22,33], resulted in new representatives of largely unexplored 0D- [6] and 1D-hybrid perovskites [11,21,34] or perovskitoids [35] with electroactive organic cations, as identified by X-ray diffraction analysis.

Materials and Methods
Synthesis. All synthetic manipulations were carried out on air unless stated otherwise. Solvents were purchased from commercial sources and purified by distilling from conventional drying agents under an argon atmosphere prior to use. Anthracene, pyrene and styrene were obtained commercially (Sigma-Aldrich). The 9-Anthracenecarboxaldehyde [36], 1-bromopyrene [37], 1-pyrenecarbaldehyde [38] and (E)-4-styrylbenzaldehyde [39] were synthesized as reported earlier, while the corresponding hydrobromides, as described in [40] (Schemes 2-4). 1 H spectra were recorded from solutions in DMSO-d6 or CDCl3 with Varian 400 Inova FT-spectrometer (Varian, Palo Alto, USA) with 400.13 MHz 1 H frequency; the measurements were done using the residual signals of these solvents ( 1 H 2.50 ppm and 7.26 ppm).
Synthesis of 9-anthracenecarboxaldehyde (Scheme 2) [36]. In a 500 mL round-bottomed flask fitted with a magnetic stir bar and reflux condenser, phosphorus oxychloride (17.5 g, 0.115 mol) and anthracene (11.25 g, 0.065 mol) were mixed with 10 mL of o-dichlorobenzene in 200 mL of DMF. The flask was heated while stirring to 90-95 °C over a period of 30 min to give a deep red solution, which was heated for 3 h and then cooled to room temperature. Upon cooling, the residual reddish oil solidified. A solution of 70 g of crystalline sodium acetate in 125 mL of water was then added to the cooled solution. The aqueous liquor was decanted. A crude solid was recrystallized from 50 mL of hot glacial acetic acid; when cold, the bright yellow aldehyde was filtered by suction, washed on the filter with 30 mL of methanol and dried in vacuum (10 mm Hq). Yield: 9.65 g (72%). 1

Materials and Methods
Synthesis. All synthetic manipulations were carried out on air unless stated otherwise. Solvents were purchased from commercial sources and purified by distilling from conventional drying agents under an argon atmosphere prior to use. Anthracene, pyrene and styrene were obtained commercially (Sigma-Aldrich). The 9-Anthracenecarboxaldehyde [36], 1-bromopyrene [37], 1-pyrenecarbaldehyde [38] and (E)-4-styrylbenzaldehyde [39] were synthesized as reported earlier, while the corresponding hydrobromides, as described in [40] (Schemes 2-4). 1 H spectra were recorded from solutions in DMSO-d 6 or CDCl 3 with Varian 400 Inova FT-spectrometer (Varian, Palo Alto, Santa Clara, CA, USA) with 400.13 MHz 1 H frequency; the measurements were done using the residual signals of these solvents ( 1 H 2.50 ppm and 7.26 ppm).

Materials and Methods
Synthesis. All synthetic manipulations were carried out on air unless stated otherwise. Solvents were purchased from commercial sources and purified by distilling from conventional drying agents under an argon atmosphere prior to use. Anthracene, pyrene and styrene were obtained commercially (Sigma-Aldrich). The 9-Anthracenecarboxaldehyde [36], 1-bromopyrene [37], 1-pyrenecarbaldehyde [38] and (E)-4-styrylbenzaldehyde [39] were synthesized as reported earlier, while the corresponding hydrobromides, as described in [40] (Schemes 2-4). 1 H spectra were recorded from solutions in DMSO-d6 or CDCl3 with Varian 400 Inova FT-spectrometer (Varian, Palo Alto, USA) with 400.13 MHz 1 H frequency; the measurements were done using the residual signals of these solvents ( 1 H 2.50 ppm and 7.26 ppm).
Synthesis of 9-anthracenecarboxaldehyde (Scheme 2) [36]. In a 500 mL round-bottomed flask fitted with a magnetic stir bar and reflux condenser, phosphorus oxychloride (17.5 g, 0.115 mol) and anthracene (11.25 g, 0.065 mol) were mixed with 10 mL of o-dichlorobenzene in 200 mL of DMF. The flask was heated while stirring to 90-95 °C over a period of 30 min to give a deep red solution, which was heated for 3 h and then cooled to room temperature. Upon cooling, the residual reddish oil solidified. A solution of 70 g of crystalline sodium acetate in 125 mL of water was then added to the cooled solution. The aqueous liquor was decanted. A crude solid was recrystallized from 50 mL of hot glacial acetic acid; when cold, the bright yellow aldehyde was filtered by suction, washed on the filter with 30 mL of methanol and dried in vacuum (10 mm Hq). Yield: 9.65 g (72%). 1   Synthesis of 1-bromopyrene (Scheme 3) [37]. In a 250 mL round-bottomed flask fitted with a magnetic stir bar, pyrene (5 g, 0.024 mol) and N-bromosuccinimide (4.4 g, 0.024 mol) were mixed in 100 mL of dichloromethane. The resulting suspension was stirred for 12 h at room temperature and then filtered while discarding the solid. The mother liquor was evaporated, and a crude solid was recrystallized from hot petroleum ether; when cold, white crystals of 1-bromopyrene were filtered by suction and dried in vacuum (10 mm Hq). Yield: 4.69 g (68%). 1   Synthesis of 1-pyrenecarbaldehyde (Scheme 3) [38]. 1-Bromopyrene (4 g, 0.014 mol, 1.0 equiv.) was put into a 250 mL one-necked round-bottomed Schlenk flask with a rubber septum equipped with a magnetic stir bar. The flask was evacuated under vacuum (10 mm Hq) and purged with nitrogen (three times). Dry THF (100 mL) was added in a nitrogen atmosphere. After cooling to −78 °C, n-BuLi (2.5 M in hexane, 7.28 mL, 0.018 mol, 1.3 equiv.) was added via a syringe over a period of 10 min to produce a light-brown solution.
After stirring for 15 min, anhydrous DMF (1.4 mL, 0.018 mol, 1.3 equiv.) was also added via a syringe, and the mixture was allowed to reach room temperature while stirring for 12 h overnight. When cooled, it was carefully poured into rapidly stirred water (100 mL), and diethyl ether (100 mL) was then added. The organic phase was separated and washed with water. After drying over MgSO4, the mixture was filtered and the solvent was re- crystalline sodium acetate in 125 mL of water was then added to the cooled solution. The aqueous liquor was decanted. A crude solid was recrystallized from 50 mL of hot glacial acetic acid; when cold, the bright yellow aldehyde was filtered by suction, washed on the filter with 30 mL of methanol and dried in vacuum (10 mm Hq). Yield: 9.65 g (72%). 1  General procedure for the preparation of amine hydrobromides (Schemes 2-4) [40]. A solution of an appropriate aldehyde (12.25 mmol, 1 equiv.) and hydroxy-ammonium chloride (1.025 g, 14.7 mmol, 1.2 equiv.) in ethanol (80 mL)wais stirred for 1 h. Then, hydrochloric acid (12 M, 4.08 mL, 4 equiv.) and zinc dust (2 g, 30.63 mmol, 2.5 equiv.) were slowly added, and the resulting mixture was stirred at room temperature for 45 min. A solution of ammonia (30%, 3.5 mL) and sodium hydroxide (6 M, 7.5 mL) was added dropwise. The mixture was stirred at room temperature for 15 min and then filtered; the solid was discarded and the mother liquor, poured into water (100 mL). The resulting suspension was extracted with dichloromethane, dried over anhydrous sodium sulfate and filtered. The solvent was removed under vacuum (10 mm Hq) to produce a solid residue that was suspended in aqueous HBr (48%) and stirred for 5 min, filtered and washed with water until the pH values reaches 7. The solid was then dried in high vacuum (1 mm Hq) and used without further purification.

Synthesis of [PyrNH3][Pb2Br6][DMFH](DMF)2.
In a 5 mL scintillation vial filled with 2 mL of DMF, pyren-4-ylmethanamine hydrobromide (15 mg, 0.0383 mmol) was mixed with PbBr2 (19 mg, 0.0383 mmol) and tetracyanoethylene (4.9 mg, 0.0383 mmol). The resulting suspension was heated until the mixture became clear. After cooling to room temperature, the vial was placed into a 20 mL vial filled with 3 mL of diethyl ether and capped tightly. Upon storing for 2 days, diethyl ether diffused into the stock solution to produce Scheme 4. Synthesis of (E)-(4-styrylphenyl)methanamonium hydrobromide, Styr NH 3 Br. [37]. In a 250 mL round-bottomed flask fitted with a magnetic stir bar, pyrene (5 g, 0.024 mol) and N-bromosuccinimide (4.4 g, 0.024 mol) were mixed in 100 mL of dichloromethane. The resulting suspension was stirred for 12 h at room temperature and then filtered while discarding the solid. The mother liquor was evaporated, and a crude solid was recrystallized from hot petroleum ether; when cold, white crystals of 1-bromopyrene were filtered by suction and dried in vacuum (10 mm Hq). Yield: 4.69 g (68%). 1  Synthesis of 1-pyrenecarbaldehyde (Scheme 3) [38]. 1-Bromopyrene (4 g, 0.014 mol, 1.0 equiv.) was put into a 250 mL one-necked round-bottomed Schlenk flask with a rubber septum equipped with a magnetic stir bar. The flask was evacuated under vacuum (10 mm Hq) and purged with nitrogen (three times). Dry THF (100 mL) was added in a nitrogen atmosphere. After cooling to −78 • C, n-BuLi (2.5 M in hexane, 7.28 mL, 0.018 mol, 1.3 equiv.) was added via a syringe over a period of 10 min to produce a light-brown solution. After stirring for 15 min, anhydrous DMF (1.4 mL, 0.018 mol, 1.3 equiv.) was also added via a syringe, and the mixture was allowed to reach room temperature while stirring for 12 h overnight. When cooled, it was carefully poured into rapidly stirred water (100 mL), and diethyl ether (100 mL) was then added. The organic phase was separated and washed with water. After drying over MgSO 4 , the mixture was filtered and the solvent was removed from the filtrate by rotary evaporation to produce an orange solid, which was then recrystallized from hot ethanol as yellow crystals. Yield: 2.06 g (64%). 1  Synthesis of (E)-4-styrylbenzaldehyde (Scheme 4) [39]. An oven-dried 350-mL Schlenk flask was charged under nitrogen with Cs 2 CO 3 (12.32 g, 0.0378 mol) and DMF (100 mL). 4-Bromobenzaldehyde (5 g, 0.027 mol) and freshly distilled styrene (3.72 mL, 0.032 mol) were added via syringes. Pd(OAc) 2 (5 mg, 0.022 mmol) in DMF (1 mL) was then added via a syringe. The Schlenk tube was sealed under argon and placed in an oil bath preheated to 140 • C. At this temperature, the reaction mixture was stirred for 19 h. When cooled to room temperature, the reaction mixture was poured into water (250 mL) and extracted with dichloromethane. The organic extract was washed with brine, dried over MgSO 4 and concentrated to dryness under vacuum (10 mm Hq). A crude product was purified by flash chromatography on silica (dichloromethane). Yield: 4.94 g (88%). 1  General procedure for the preparation of amine hydrobromides (Schemes 2-4) [40]. A solution of an appropriate aldehyde (12.25 mmol, 1 equiv.) and hydroxy-ammonium chloride (1.025 g, 14.7 mmol, 1.2 equiv.) in ethanol (80 mL)wais stirred for 1 h. Then, hydrochloric acid (12 M, 4.08 mL, 4 equiv.) and zinc dust (2 g, 30.63 mmol, 2.5 equiv.) were slowly added, and the resulting mixture was stirred at room temperature for 45 min. A solution of ammonia (30%, 3.5 mL) and sodium hydroxide (6 M, 7.5 mL) was added dropwise. The mixture was stirred at room temperature for 15 min and then filtered; the solid was discarded and the mother liquor, poured into water (100 mL). The resulting suspension was extracted with dichloromethane, dried over anhydrous sodium sulfate and filtered. The solvent was removed under vacuum (10 mm Hq) to produce a solid residue that was suspended in aqueous HBr (48%) and stirred for 5 min, filtered and washed with water until the pH values reaches 7. The solid was then dried in high vacuum (1 mm Hq) and used without further purification.

Synthesis of [AntrNH 3 ][PbBr 3 ](DMF).
In a 5 mL scintillation vial filled with 2 mL of DMF, anthracen-9-ylmethanamine hydrobromide (10 mg, 0.0347 mmol) was mixed with PbBr 2 (12.7 mg, 0.0347 mmol) and tetracyanoethylene (4.4 mg, 0.0347 mmol). The resulting suspension was heated until the mixture became clear. After cooling to room temperature, the vial was placed into a 20 mL vial filled with 3 mL of diethyl ether and capped tightly. Upon storing for 2 days, diethyl ether diffused into the stock solution to produce nearly transparent pale-yellow needle-like crystals. Yield: 15 mg (52%). Anal. Calc. for C 18 2 , at 120 K with a Bruker APEX2 DUO CCD diffractometer (Bruker AXS, Karlsruhe, Germany), both using the graphite monochromated Mo-Kα radiation (λ = 0.71073 Å). Using Olex2 [41], the structures were solved with the ShelXT structure solution program [42] using Intrinsic Phasing and refined with XL refinement package [43] using Least Squares minimization. Hydrogen atoms of NH 3 groups were located in different Fourier synthesis. Positions of other hydrogen atoms were calculated, and they all were refined in the isotropic approximation in the riding model. Disordered solvent molecules of DMF and dichloromethane occupying the same positions in the crystal of [Styr-NH 3 ] 2 [PbBr 4 ] have been treated as a diffuse contribution to the overall scattering without specific atom positions by SQUEEZE/PLATON [44]. Crystal data and structure refinement parameters are given in Table 1

Results and Discussion
The organic donors (anthracene, pyrene and (E)-stilbene) to form a charge-transfer complex with TCNE were functionalized by a methanamine group to function as organic cations in the hybrid perovskites based on lead(II) bromide. The corresponding hydrobromides AntrNH 3 Br, PyrNH 3 Br and StyrNH 3 Br (Scheme 1) were synthesized in satisfactory yields from related aldehydes by their "one-pot" reductive amination with hydroxyl amine, metal zinc and hydrochloric acid in ethanol and a treatment of the resulting products with hydrobromic acid [40]. Although performing this reaction in two steps gives a 10%-increase in the yield [29], such a "one-pot" procedure facilitates the workup. Anthracene-9-carbaldehyde was obtained by a modified Vilsmeier-Haak procedure [36] (Scheme 2), while 1-pyrenecarbaldehyde, by formylation via lithiation of 1-pyrene bromide and the subsequent reaction with DMF [38,45] (Scheme 3). For (E)-4-styrylbenzaldehyde, a different approach was used [39], the Heck coupling reaction [39] of 4-bromobenzaldehyde and styrene (Scheme 4).
Each hydrobromide was then dissolved in hot DMF together with PbBr 2 and TCNE in a ratio of 1:1:1, following a strategy successfully employed to obtain lead bromide-based perovskites with an organic charge-transfer complex between a pyrene donor and 7,7,8,8tetracyanoquinodimethane (TCNQ) acceptor [21][22][23]. Attempts to use other high-boiling polar solvents that provided a similarly good solubility of both organic and inorganic reagents (i.e., DMSO and glycerol) produced oily products upon vapor diffusion of diethyl ether into the solutions. In contrast, the crystallization from DMF under the same conditions readily (in a two-day period) resulted in nearly transparent pale-yellow needle-like crystals, which were collected by filtration. We expected them to be new 1D- [21] or 2D- [22,23] hybrid perovskites that contained organic charge-transfers complexes with TCNE; however, the latter was not detected by X-ray diffraction (Figures 1-3). Instead, the obtained crystalline products were perovskitoids [35] with the corresponding methanamonium cations and one-dimensional (1D) or finite arrays of lead bromide octahedra connected via different modes (other than corner-sharing in true perovskites [35]) depending on the polyaromatic/conjugated core in the hydrobromide used.   (11) 3.537 (7) 3.232(14)-3.701(13) Switching to (E)-(4-styrylphenyl)methanamonium hydrobromide as a source of a potential organic donor that has a very different (elongated) shape from the above "compact" polyaromatic compounds resulted in a completely different, although low-dimensional (0D) [13] (Figure 3b). These mini-rods are made from four lead bromide octahedra that are only slightly distorted ( Table 2) and feature yet another binding mode, as they share in the order of a face, an edge and a face (Figure 3a) similar to an octahedra sharing sometimes found in 1D hybrid perovskitoids [35], such as corner-shared mini-rods in a previously reported bromoplumbate with a Nmethylated 4,4′-bipyridine cation [50]. Note that other 0D-perovskitoids often (incorrectly) [51] referred to as 0D-perovskites [13] contain isolated octahedral anions MX6 (M = Pb 2+ , Sn 2+ , Bi 3+ ; X = Cl−, Br−, I−) or their face-shared dimers [13] or trimers [35].
In [StyrNH3]2[PbBr4], the mini-rods [Pb4Br16] 8+ that can be thought of as two such dimers edge-shared together are decorated and connected by numerous hydrogen bonds with the ammonium groups of the eight symmetry-independent cations (N…Br 3.232(14)-3.812(13) Å, NHBr 119(1)-172(1)) to give H-bonded layers parallel to the crystallographic plane ab. Within these layers, the mini-rods are additionally connected  (Figure 1) with two symmetry-independent anthracen-9-ylmethanamonium cations, AntrNH 3 + , and two solvent DMF molecules in an asymmetric unit features 1D ladder-like double chains along the crystallographic axis a (Figure 1 top) that are made of nearly ideal octahedra, as quantified by a continuous symmetry measure [46] (Table 2), of lead bromide (Pb-Br 2.8402(11)-3.2532(13) Å). Each octahedron is edge-shared to four others in a rare manner found in [47] (Figure 1 bottom).
On the opposite sides, these 1D ladder-like chains are decorated by the organic cations that each form two hydrogen bonds (N . . . In the resulting H-bonded columns, the anthracene cores of the cations are parallel and only 3.419(9) and 3.464(9) Å apart. The π-π stacks that they form on each side of the 1D ladder-like chains of lead bromide units in [AntrNH 3 ][PbBr 3 ](DMF) run along these chains owing to the ammonium group significantly deviating from the aromatic plane (Figure 1, top); the corresponding angle between the plane and the bond C-N is 115.2(7) and 115.8(7) • in two symmetry-independent cations. Such a packing motif is additionally stabilized by C-H . . . π interactions between the methylene bridges and the anthracene cores of the neighboring cations. The columns are rotated by 78.95(3) • relative to each other (Figure 1, bottom) and are held together only by weak interactions, such as C-H . . . π The layers are packed into a dense 3D-framework by weak C-H…π interactions between the interdigitated 4-styrylphenyl-based cations from the neighboring layers ( Figure  3b), thus mirroring a bilayered structure [52] typical of ionic liquid crystals [53] with heterocyclic cations featuring long non-polar alkyl chains. As in the latter case [53], there are no stacking interactions between the conjugated 4-styrylphenyl cores in the bilayers. In contrast, they are nearly perpendicular to each other, which is facilitated by their molecular geometry. Thanks to an elongated shape of the 4-styrylphenyl core, the alkylammonium group does not have to significantly (by 115.2(7)-115. 8
Of In the resulting columns that are decorated from one side by the pyrene cations, the DMF molecules are sandwiched between these cations so that no stacking interactions occur between them; the distance between the centroids of the pyrene core and that of the C 2 NCO plane of the DMF molecule tilted by 8. Switching to (E)-(4-styrylphenyl)methanamonium hydrobromide as a source of a potential organic donor that has a very different (elongated) shape from the above "compact" polyaromatic compounds resulted in a completely different, although low-dimensional (0D) [13] (Figure 3 bottom). These mini-rods are made from four lead bromide octahedra that are only slightly distorted (Table 2) and feature yet another binding mode, as they share in the order of a face, an edge and a face (Figure 3 top) similar to an octahedra sharing sometimes found in 1D hybrid perovskitoids [35], such as corner-shared mini-rods in a previously reported bromoplumbate with a N-methylated 4,4 -bipyridine cation [50]. Note that other 0D-perovskitoids often (incorrectly) [51] referred to as 0D-perovskites [13] contain isolated octahedral anions MX 6 (M = Pb 2+ , Sn 2+ , Bi 3+ ; X = Cl − , Br − , I − ) or their face-shared dimers [13] or trimers [35].
In  (12) Å) between the bromide anions that assemble them into pseudo-2D arrays of lead bromide octahedra.
The layers are packed into a dense 3D-framework by weak C-H . . . π interactions between the interdigitated 4-styrylphenyl-based cations from the neighboring layers (Figure 3 bottom), thus mirroring a bilayered structure [52] typical of ionic liquid crystals [53] with heterocyclic cations featuring long non-polar alkyl chains. As in the latter case [53], there are no stacking interactions between the conjugated 4-styrylphenyl cores in the bilayers. In contrast, they are nearly perpendicular to each other, which is facilitated by their molecular geometry. Thanks to an elongated shape of the 4-styrylphenyl core, the alkylammonium group does not have to significantly (by 115.2(7)-115.8 (7)  Note that in all cases, the presence of TCNE in the reaction mixture did not stir the outcome towards the above crystalline products, the 1D-hybrid perovskitoids [ ]. Indeed, omitting it while keeping the same concentrations of lead bromide and the corresponding hydrobromide in DMF, which was the best solvent for this purpose, did not change the result for any of the probed cations. The use of other popular organic acceptors, such as 7,7,8,8-tetracyanoquinodimethane (TCNQ), 1,2,4,5-tetracyanobenzene, hexafluorobenzene, chrolanil or 1,4-benzoquinone, also produced the same 0D-and 1D-hybride perovskitoids and, sometimes, side-products, such as previously reported [29] lead(II) bromide with DMF PbBr 2 (DMF). Those were also obtained when anti-solvents different from diethyl ether (e.g., dichloromethane or pentane) or other ratios of the reagents were used, such as donor: PbBr 2 : acceptor ratios of 1:1:1, 2:1:1 and 1:1:5.

Conclusions
In our search for low-dimensional hybrid perovskites with organic charge-transfer complexes to tune their optoelectronic properties for use in solar cells [21][22][23][24]33], new pseudo-layered 0D-and 1D-hybrid perovskitoids [35] (often incorrectly [51] referred to as perovskites) were obtained from lead bromide. They were identified by X-ray diffraction to contain the lead bromide octahedral anions featuring different sharing modes and the alkylammonium cations, the derivatives of aromatic and conjugated molecules common for organic charge-transfer complexes (anthracene, pyrene and (E)-stilbene).
The lack of an organic acceptor may result from steric or electronic effects of the ammonium group that is H-bonded to the lead bromide chains or mini-rods in these 1D-and 0D-hybrid perovskitoids. In the corresponding cations, the ammonium group is separated from the aromatic or conjugated cores only by a methylene bridge, so it may preclude an organic acceptor, even a small TCNE molecule, from approaching these cores or make them electron donors that are not good enough for many other acceptors to form a charge-transfer complex. An experimental piece of evidence is a successful self-assembling of 1D-and 2D-hybrid perovskites under similar conditions by using a functionalized pyrene donor with a longer alkyl chain, pyrene-4-ylbutanamine [21][22][23].
Although for these reasons we failed to synthesis the low-dimensional hybrid perovskites with organic charge-transfer complexes for solar cells, the obtained 1D-hybrid perovskitoids [ 4 ] with unusual mini-rods of four face-and edge-shared octahedra can be of use in another type of optoelectronic device, [55,56] photodetectors; [57] testing them for this application is underway in our group.