Fluoroiodate

A fluorooxoiodate or fluoroiodate is a chemical compound or ion derived from iodate, by substituting some of the oxygen by fluorine. They have iodine in the +5 oxidation state. The iodine atoms have a stereochemically active lone-pair of electrons. Many are non-centrosymmetric, and are second harmonic generators of intense light shining through them. They are under investigation as materials for non-linear optics, such as for generating ultraviolet light from visible or infrared lasers.
Different ions include ⁻, ⁻, ²⁻, and ²⁻.
They are distinct from the iodate fluorides which are mixed anion compounds that do not have fluorine-iodine bonds.

Properties

Fluoroiodates are transparent in visible, longer wave ultraviolet and some of the infrared electromagnetic bands.
Compared to iodate, the I-O bonds are shorter, and I-F bonds are longer in fluoroiodates. The I-F bond is about 0.2 Å longer than the I-O bond. The fluorine atoms repel each other in ⁻ and are almost opposite each other. The ∠OIF angle is close to 90° and the oxygen atoms ∠OFO are at about 102°, so they resemble an octahedral arrangement, with two adjacent positions deleted.

List

formula	crystal	space group	unit cell	volume	density	band gap eV	SHG × KDP 1064 nm	comment	reference
NH₄IO₂F₂	orthorhombic	Pca2₁	a=8.639 b=6.166 c=8.629 Z=4	459.7		4.53	1.2
₃₃·H₂O	orthorhombic	Pnma	a=15.102 b=12.685 c=7.369 Z=4	1411.8		4.55	no
⁺^–	triclinic	P	a = 6.6890 b = 10.2880 c = 10.30.92 α = 105.447 β = 108.568 γ = 91.051° Z=4	644.08	2.650	4.81		explosive; birefringence Δn = 0.110
₂	monoclinic	P2₁/c	a=7.4388 b=19.2679 c=11.0753 β=106.289° Z=4	1523.70		4.49		birefringence Δn = 0.068
NaIO₂F₂	orthorhombic	Cmcm	a=6.929 b=7.274 c=7.350 Z=4	370.42			0
KIO₂F₂	orthorhombic	Pca2₁	a=8.3943 b=5.9792 c=8.4468 Z=4	423.95			0	ferroelastic; when compressed on 001 axis IO₂F₂ units rotate with abc transforming to cba;
CoIO₃F	monoclinic	P2₁/n	a=4.9954 b=5.2110 c=12.5179 β=95.347°
NiIO₃F	monoclinic	P2₁/n
ZnIO₃F	monoclinic	P2₁/m				4.2	0.00	birefringence 0.219 at 546 nm
	orthorhombic	Pca2₁	a=13.954 b=6.9261 c=4.7629			4.34	10	laser [damage threshold] 298.40 MW cm⁻²; decompose 300 °C; dipole moment density: 0.0908 D Å⁻³
NaGaI₃O₉F	monoclinic	P2₁/c	_a=14.120 b=4.9149 c=13.63 β=112.968° Z=4	871.0	4.853	4.27	0	_∞²⁻ layers sandwiching Na⁺; birefringence Δn_exp ~ 0.203 at 1064 nm
RbIO₂F₂	orthorhombic	Pca2₁	a=8.567 b=6.151 c=8.652 Z=4	455.92		4.2	4
SrI₂O₅F₂	monoclinic	P2₁/c	a=10.462 b=7.272 c=8.306 β=109.699° Z=4	594.9		3.68	0
Sr₄O₃BF₄		R3''c	a''=9.7216 c=38.759					absorption band at 250 nm; decompose 380 °C
CdIO₃F		P2₁2₁2₁				4.22	6.2
Rb₂MoO₂F₃	orthorhombic	Cmc2₁	a 11.806 b 10.128 c 7.6661			3.77	5
CsIO₂F₂	orthorhombic	Pca2₁	a=8.781 b=6.377 c=8.868 Z=4	496.58		4.5	3
Cs₃₃•H₂O		Pnma				3.37	0
Cs₂•H₂O•H3O	monoclinic	P2₁/c				2.77	0
CsIO₄		Pnma					0
Cs₂VOF₄	orthorhombic	Cmc2₁	a=12.188 b=10.349 c=7.779 Z=4	981.2	4.100	2.88	5	yellow at 1064 nm
Cs₂MoO₂F₃	orthorhombic	Cmc2₁	a =12.2153 b =10.4656 c =7.8560			3.43	4.5
BaIO₃F	monoclinic	P2₁/c				4.32	0
Ba₂	monoclinic	P2₁/c	a=10.747 b=7.161 c=9.086 β=93.748° Z=4	697.7		3.99	0	UV cut off 230 nm
BaI₂O₅F₂	monoclinic	P2₁/c	a=10.750 b=7.599 c=8.598 β=109.753°					birefringence Δn= 0.174 at 1064 nm
BaIO₂F₃	orthorhombic	Cmca	a=6.334 b=6.343 c=23.300			4.27	0	birefringence Δn=0.133 at 1064 nm
Ba₂	monoclinic	P2₁/c	a=7.5065 b=7.4160 c=14.5932 β=100.363°					birefringence Δn=0.068 at 550 nm; UV edge 230 nm; transparent 0.34–11.9 μm
CaCe₃F	orthorhombic	Pna2₁	a=11.068 b=18.15 c=6.0301 Z=4	1211.3	5.033	2,72	5	pale-yellow; birefringence 0.071 at 1064 nm SHG 5×KDP at 1064 nm
Rb₂WO₂F₃	orthorhombic	Cmc2₁	a=11.726 b=10.188 c=7.666			4.42
Cs₂WO₂F₃	orthorhombic	Cmc2₁	a=12.1122 b=10.6192 c =7.8333			4.29
Pb₄O₃BF₄		R3''c	a'' =9.8184 c =38.867					absorption band at 283 nm; decomposes 300 °C