Related Experiment Video
Updated: Jul 22, 2026
Monovalent Cation Doping of CH3NH3PbI3 for Efficient Perovskite Solar Cells
Published on: March 19, 2017
Crystal Structures and Magnetic Properties of a Novel Layer Perovskite System: (3-Picoliniumylammonium)CuX(4) (X =
Greg S. Long1, Mingyi Wei, Roger D. Willett
1Department of Chemistry, Washington State University, Pullman, Washington 99164.
Abstract:
The compounds (C(6)N(2)H(10))CuX(4), where the cation is diprotonated 3-picolylamine and X = Cl(-) or Br(-), form an unusual variant of the normal antiferrodistortive A(2)CuX(4) lattice [(C(6)N(2)H(10))CuCl(4), orthorhombic, Pna2(1), a= 7.747(1), b = 24.960(2), and c = 17.041(1) Å, Z = 12; (C(6)N(2)H(10))CuBr(4), orthorhombic, Pna2(1), a = 8.133(1), b= 26.129(1), and c = 17.148(1) Å, Z = 12]. The structures contain ribbons of the antiferrodistortive sheets which are six copper atoms wide. The central four Cu(II) ions have the usual elongated octahedral coordination, while on each edge are CuX(4)(2)(-) ions which have a distorted tetrahedral geometry. Long Cu.X interactions (4.000 and 4.124 Å for the Cl and Br salts, respectively) between these terminating anions link the ribbons together into sheets. The organic cations provide overall stability to the lattice and link adjacent sheets together, forcing the existence of short two-halide X.X contacts between sheets (average Cl.Cl = 4.629 Å, Br.Br = 4.425 Å). While the changes in the semicoordinate Cu.X distances upon replacement of Cl by Br mirror the change in ionic radius, the X.X distances actually decrease when the larger bromide ion is introduced. This is because these distances are largely dictated by the size of the organic cation. The magnetic data for both salts show the presence of predominant ferromagnetic interactions at high temperature. The Cl salt orders antiferromagnetically at T(c) = 5.7 K, and the susceptibility data can be fit to a S = (1)/(2) Heisenberg model for antiferromagnetically coupled ferromagnetic layers with a mean in-plane exchange constant of J/k = 8.13 K and an interlayer exchange constant of J'/k = 1.22 K. The corresponding values for the Br salt are T(c) = 18.9 K, J/k = 21.3 K, and J'/k = 5.87 K The increase in magnitude of the exchange constants and ordering temperature of the Br salt relative to the Cl salt is consistent with the increase in ionic radius of Br(-) relative to Cl(-).
Related Concept Videos
02:42Ionic Crystal Structures
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:37Metallic Solids
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability. Many...
02:42Valence Bond Theory
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:18Unit Cells