The structures, optical properties, and field-effect mobilities of three se
miconducting m-fluorophenethylammonium-based (C6H4FC2H4NH3)(2)SnI4 perovski
tes (m = 2, 3, or 4) are reported and compared with the analogous measureme
nts for the nonfluorosubstituted phenethylammonium system, (C6H5C2H4NH3)(2)
SnI4. The (4-fluorophenethylammonium)(2)SnI4 system adopts a fully ordered
monoclinic (P2(1)/c) cell with the lattice parameters a = 16.653(2) Angstro
m, b = 8.6049(8) Angstrom, c = 8.7551(8) Angstrom, beta = 98.644(2)degrees,
and Z = 2. Both (3-fluorophenethylammonium)(2)SnI4 and (2-fluorophenethyla
mmonium)(2)SnI4 are refined in a monoclinic C2/c subcell with the lattice p
arameters a = 34.593(4) Angstrom, b = 6.0990(8) Angstrom, c = 12.254(2) Ang
strom, beta = 103.917(2)degrees, and Z = 4 and a = 35.070(3) Angstrom, b =
6.1165(5) Angstrom, c = 12.280(1) Angstrom,beta = 108.175(1)degrees, and Z
= 4, respectively. Each hybrid structure consists of sheets of corner-shari
ng distorted SnI6 octahedra separated by bilayers of fluorophenethylammoniu
m cations. The dominant low energy feature in the optical absorption spectr
a for spin-coated films of the new hybrids (an exciton band associated with
the tin(II) iodide framework) shifts from 609 to 599 nm and 588 nm across
the series m = 4 to 2 (the corresponding value for the phenethylammonium-ba
sed system is 609 nm). This shift in optical properties is primarily attrib
uted to subtle structural modifications induced by the organic cation subst
itutions, including a progressive shift in Sn-I-Sn tilt angle between adjac
ent SnI6 octahedra from 156.375(8)degrees for the m = 4 structure to 154.16
(3)degrees and 153.28(3)degrees (average) for the m = 3 and 2 structures, r
espectively. The corresponding angle in the previously reported phenethylam
monium-based structure is 156.48 degrees (average), very similar to the M =
4 value. Other potentially important structural modifications include the
average Sn-I bond length and the degree of interaction between the substitu
ted fluorine and the inorganic sheet. Saturation regime field-effect mobili
ties for thin-film field-effect transistors based on the new fluorophenethy
lammonium-based hybrids are similar to that previously observed in (pheneth
ylammonium)(2)SnI4, typically ranging from similar to0.2 to 0.6 cm(2) V-1 s
(-1), with the maximum currents in the devices decreasing across the series
m = 4 to 2. The differences in transport properties can be attributed to t
he change in electronic structure, as well as to film morphology modificati
on, brought about by the organic cation substitutions.