of 148
S
1
Supporting Information
Boronated Cyanometallates
Brendon J. McNicholas
*
1
, Cherish Nie
1
, Anex Jose
3
, Paul H. Oyala
1
,
Michael
K
. Takase
1
, La
wrence
M
.
Henling
1
,
Alexandra T. Barth
1
,
Alessio Amaolo
1
,
Ryan G. Hadt
1
,
Edward I. Solomon
2
,
Jay R. Winkler
1
,
Harry B. Gray
1
*
, and Emmanuelle Despagnet
-
Ayoub
3
*
1.
Division of Chemistry and Chemical Engineering,
California Institute of Technology,
1200 East California Boulevard, Mail
Code 139
-
74, Pasadena,
California
91125,
United States of America
2
. Department of
Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305
-
5080, United States of America
3
. Department of Chemistry, Occidental College, 1600 Campus Road, Los Angeles, California 90041, United States of Americ
a
*
co
-
Corresponding
Author
s
:
bmcnicho@caltech.edu@caltech.edu
,
hbgray@caltech.edu
,
edespagnetay@oxy.edu
Table of Contents
Page Number
S.1. General
S
2
S.2. NMR Spectra
S
1
5
S.3
. Infrared Spectra
S
3
2
S.4. UV
-
v
is
-
NIR Spectra
S
4
0
S.5. Magnetic Circular
Dichroism Spectr
a
S
5
1
S.6. Gaussian Deconvolution of Magnetic Circular Dichroism Spectra
and UV
-
vis
-
NIR Spectra
S
6
2
S.
7
. Electrochemistry
S
8
8
S.8.
Spectroelectrochemistry Spectra
S
9
6
S.9. Luminescence Spectra
S
9
7
S.
10
. EPR Spectra
S
99
S.
11
.
X
-
Ray Crystallographic Data
S
10
3
S.1
2
. DFT/CASSCF+NEVPT2
Inputs
S
14
5
S.1
3
. References
S
14
7
S
2
S.1. General
Potassium hexacyanoferrate(III) (K
3
[Fe(CN)
6
])
(Sigma
-
Aldrich), bis(triphenylphosphine)iminium
chloride (PPNCl) (Sigma
-
Aldrich), potassium hexacyanoferrate(II) (K
4
[Fe(CN)
6
]) (Sigma
-
Aldrich), potassium hexacyanomanganate(III) (Sigma
-
Aldrich), potassium hexachloroosmate(IV)
(Sigma
-
Aldrich), potassium cya
nide (Sigma
-
Aldrich), ruthenium trichloride (Sigma
-
Aldrich),
elemental bromine (Sigma
-
Aldrich), tris(pentafluorophenyl)borane (TCI Chemicals), poly(methyl
methacrylate) (Sigma
-
Aldrich), tetraphenylarsonium chloride (Sigma
-
Aldrich/Strem Chemicals),
and tetr
aphenylphosphonium chloride (Sigma
-
Aldrich) were used as received.
Tetrabutylammonium bromide (Avocado Chemicals), tetrabutylammonium chloride (Sigma
-
Aldrich), ceric ammonium nitrate (Sigma
-
Aldrich), cerium sulfate (Sigma
-
Aldrich), potassium
graphite (Stre
m Chemicals, Inc.), 18
-
crown
-
6 ether (Sigma
-
Aldrich), and cobaltocene (Sigma
-
Aldrich) were used as received.
Tris(2,4,6
-
trifluorophenyl)borane was synthesized according to
literature precedent.
1,2
Triphenylborane
(Sigma
-
Aldrich) was purified according to literature
precedent.
3
Solvents were obtained from degassed, dry solvent systems. All boronations were
performed in a nitrogen
-
filled glove box. K
4
[Os(CN)
6
]
4
and K
4
[Ru(CN)
6
]
5
were synthesized
according to literatu
re precedent (
CAUTION
: KCN at reflux and
/or
at neutral or acidic pH has
the potential to evolve hydrogen cyanide gas
.
Always perform in a closed fume hood and neutralize
KCN waste after synthesis). (TBA)
3
[Fe(CN)
6
],
6
(Ph
4
P)
3
[Os(CN)
6
],
7,8
(Ph
4
As/Ph
4
P)
3
[Ru(CN
)
6
],
7
(PPN)
4
[Fe(CN)
6
],
3,9
(TBA)
3
[Ru(CN)
6
],
7,10,11
(TBA)
4
[Ru(CN)
6
],
5
(TBA)
3
[Os(CN)
6
],
7
(TBA)
4
[Os(CN)
6
],
3,1
2
(TBA)
3
[Cr(CN)
6
],
1
3
(Ph
4
As)
3
[Cr(CN)
6
],
13
(TBA)
3
[Mn(CN)
6
],
14,15
(PPN)
3
[Mn(CN)
6
],
14,15
and (TBA)
4
[Fe(CN
-
B(C
6
F
5
)
3
)
6
] (
Fe
-
II
-
BCF
)
3
were
synthesized according
to literature precedent. (Ph
4
As/TBA)
3
[Cr(NC
-
BPh
3
)
6
] was synthesized according to literature
precedent
,
16
beginning with (Ph
4
As/TBA)
3
[Cr(CN)
6
] instead of (TEA)
3
[Cr(CN)
6
].
P
ropionitrile
(Sigma
-
Aldrich) were dried over 3
Å molecular siev
es and stored in a dry room or in a nitrogen
-
filled glove box. Deuterated solvents were dried and stored over activated
3
Å molecular sieves in
a nitrogen
-
filled glove box. All
NMR spectra were collected on a Varian 400 MHz spectrometer
or Bruker 400 MHz s
pectrometer (
in ppm, m: multiplet, s: singlet, d: doublet, t: triplet, pt:
pseudo
-
triplet).
13
C NMR and
31
P NMR were
1
H decoupled.
31
P NMR spectra were externally
referenced to 85% H
3
PO
4
,
19
F NMR spectra were externally referenced to neat CFCl
3
, and
11
B
NMR were internally referenced to 15% BF
3
·Et
2
O. Elemental Analyses were performed on a
PerkinElmer 2400 Series II CHN Elemental Analyzer. UV
-
visible
-
NIR spectra were recorded on
S
3
either a Cary 500 UV
-
Vis
-
NIR or HP 8453 spectrophotometer.
All room
-
temperature UV
-
vis
-
NIR
spectra and low
-
temperature magnetic circular dichroism spectra of new compounds were
deconvolved simultaneously using Gaussian
functions
with fixed absorption maxima
if possible
or by letting values float within 10% for each set of
spectra
.
All deconvolution
s
were performed
in Matlab 2018b.
Magnetic Circular Dichroism Spectroscopy
Room
T
emperature MCD Spectra:
Magnetic c
ircular dichroism data in the UV
-
vis region (300
-
800 nm) were collected on an Olis
DSM 172 spectrophotometer operating with a 9798B series S20 PMT detector and 150 W xenon
lamp power supply. The spectra were recorded at 293 K in a 1 cm path length borosili
cate cuvette
in a 1.4 T max field sample holder
. Measurements were recorded over 16 scans, with an 8 nm
measurement bandwidth.
Low Temperature MCD Spectroscopy
:
Low temperature
MCD measurements were performed on a Jasco
J810 (UV
-
Vis) and
J730
(NIR)
spe
ctropolarimeter (
NIR
: liquid
nitrogen
-
cooled InSb detection and
UV
-
Vis: S20 PMT detection)
equipped with an Oxford Instruments SM4000
-
7 T superconducting magneto
-
optical dewar.
All
MCD samples were immobilized in PMMA except for
[
Ru
III
(CN
-
B
(C
6
F
5
)
3
)
6
]
3
and
[Mn
III
(
CN
)
6
]
3
,
which were mulled with fluorolube. The
sample cells
were constructed with
two quartz disks
separated by a Viton O
-
ring spacer
.
The sample temperature was measured with a calibrated
Cernox resistor (Lakeshore Cryogenics) inserted into th
e MCD cell. The data were corrected for
zero
-
field baseline effects induced by glass cracks by subtracting the 0 T scan. The final data
reported are an average of the positive and negative field data
.
Luminescence Spectroscopy
Low temperature luminescence
spectra were recorded on an Ocean
Optics spectrometer. Low
temperature luminescence spectra were recorded on a Melles
-
Griot 13 FOS 200 spectrometer
coupled to a fiber optic cable which collected sample luminescence. Samples were excited with a
365 nm Thor
labs, Inc. UV LED (M365L1) and Thorlabs, Inc. LED driver (LEDD1) or the 3
rd
(355
nm) or 4
th
(266 nm) harmonic of a Nd:YAG laser. Long pass filters were used to isolate
S
4
luminescence signals from LED light. An Edwards T
-
Station turbo pump coupled to a radiat
ion
-
shielded cold head were used to mount the sample and apply dynamic vacuum. The sample was
cooled using a CTI
-
Cryogenics compressor. Samples were allowed to evacuate for at least fifteen
minutes prior to cooling.
Electron Paramagnetic Resonance Spect
roscopy
Continuous wave X
-
band EPR spectra were obtained on a Bruker EMX spectrometer on
1.0
-
3
.
0
mM solutions prepared as frozen
solutions
in 2
-
MeTHF
, THF, or dichloromethane
. Pulse EPR
spectroscopy: All pulse X
-
and Q
-
band (9.4
-
9.7 and 34 GHz,
respectively) EPR
and hyperfine
sublevel correlation spectroscopy (HYSCORE) experiments were acquired using a Bruker
ELEXSYS E580 pulse EPR spectrometer. All Q
-
band experiments were performed using a Bruker
D2 pulse ENDOR resonator. X
-
band HYSCORE experime
nts were performed using a Bruker MS
-
5 resonator. Temperature control was achieved using an ER 4118HV
-
CF5
-
L Flexline Cryogen
-
Free VT cryostat manufactured by ColdEdge equipped with an Oxford Instruments Mercury ITC
temperature controller.
X
-
band and Q
-
ban
d Pulse HYSCORE spectra were acquired using the 4
-
pulse sequence (
/
2−
/
2 −
1
2
/
2 − echo), where
is a fixed delay, while
!
and
"
are independently
incremented by
#
!
and
#
"
, respectively. The time domain data was baseline
-
co
rrected (third
-
order polynomial) to eliminate the exponential decay in the echo intensity, apodized with a
Hamming window function, zero
-
filled to eight
-
fold points, and fast Fourier
-
transformed to yield
the 2
-
dimensional frequency domain.
In general, the
ENDOR spectrum for a given nucleus with spin
= 1⁄2 (
19
F) coupled to the S = 1⁄2
electron spin exhibits a doublet at frequencies,
±
=
*
2
±
%
*
(
S.1
)
where
±
is the nuclear Larmor frequency and
is the hyperfine coupling. For nuclei with
≥ 1
(
14
N,
11
B), an additional splitting of the
±
manifolds is produced by the nuclear quadrupole
interaction (P).
S
5
±
,
'
#
=
*
%
±
3
(
2
(
1
)
2
*
(
S.2
)
In HYSCORE spectra, these signals manifest as
cross
-
peaks or ridges in the 2
-
D frequency
spectrum which are generally symmetric about the diagonal of a given quadrant. This technique
allows hyperfine levels corresponding to the same electron
-
nuclear submanifold to be
differentiated, as well as separat
ing features from hyperfine couplings in the weak
-
coupling regime
(|
| < 2|
l
|) in the (+,+) quadrant from those in the strong coupling regime (|
| > 2|
l
|) in the (−,+)
quadrant. The (−,−
) and (+,−) quadrants of these frequency spectra are symmetric to the (+,+) and
(−,+) quadrants, thus typically only two of the quadrants are typically displayed in literature. For
systems with appreciable hyperfine anisotropy in frozen solutions or solids
, HYSCORE spectra
typically do not exhibit sharp cross peaks, but show ridges that represent the sum of cross peaks
from selected orientations at the magnetic field position at which the spectrum is collected. The
length and curvature of these correlation
ridges allow for the separation and estimation of the
magnitude of the isotropic and dipolar components of the hyperfine tensor, as shown in
Figure
S1
.
Figure
S1
. HY
SCORE patterns for an
S
= 1/2,
I
= 1/2 spin
system with an axial hyperfine tensor which contains
isotropic (
iso
) and dipolar (
) contributions. Blue
correlation ridges
represent the strong coupling case; red
correlation ridges represent the weak coupling case.
S
6
For systems coupled to nuclei with
= 1, such as
14
N, the double
-
quantum peaks are often the
most intense feature. These cross
-
peaks are defined by the following
equations,
)
=
±
2
8
(
(
+
/
2
)
"
+
"
(
3
+
"
)
*
=
±
2
8
(
(
/
2
)
"
+
"
(
3
+
"
)
(
S
.
3
)
where
=
2
푞푄
/
4ħ. For weakly coupled nuclei (
<
2
+
)
)
and
*
are both positive, appearing
in the (+,+) quadrant, while for strongly coupled nuclei (
<
2
+
) they will show up in the (−,+)
quadrant. In the intermediate coupling regime where
2
+
, peaks will often appear in both the
(+,+) and (−,+) quadrants of the HYSCORE spectrum.
All EPR spectra (CW, ENDOR, HYSCORE) were simulated using the EasySpin si
mulation
toolbox (version 5.2.
33
)
17
with Matlab 20
20b
using the following Hamiltonian,
D
=
,
G
-
K
+
%
%
G
-
K
+
K
K
+
K
K
(
S
.
4
)
In this expression, the first term corresponds to the electron Zeeman interaction term where
,
is
the Bohr magneton,
is the electron spin g
-
value matrix with princip
al
components g = [g
xx
g
yy
g
zz
], and
K
is the electron spin operator; the second ter
m corresponds to the nuclear Zeeman
interaction term where
%
is the nuclear magneton,
%
is the characteristic nuclear g
-
value for
each nucleus (e.g.
19
F,
14
N,
11
B) and
K
is the nuclear spin operator; the third term corresponds to
the electron
-
nuclear hyperfine term, where
is the hyperfine coupling tensor with princip
al
components
= [A
xx,
A
yy,
A
zz
]; and for nuclei with
≥ 1, the final term corresponds to the
nuclear
quadrupole (NQI) term which arises from the interaction of the nuclear quadrupole
moment with the local electric field gradient (efg) at the nucleus, where
is the quadrupole
coupling tensor. In the principal axis system (PAS),
is traceless and param
etrized by the
quadrupole coupling constant
2
푄푞
/
h and the asymmetry parameter
such that
,
=
P
..
0
0
0
//
0
0
0
00
R
=
"
푄푞
/
4
(
2
1
)
T
(
1
)
0
0
0
(
1
+
)
0
0
0
2
U
(
S
.
5
)
S
7
where
1
"
23
4
=
2
(
2
1
)
00
and
=
5
$$
6
5
%%
5
&&
.
The asymmetry parameter may have values between
0 and 1, with 0 corresponding to an electric field gradient with axial symmetry and 1 corresponding
to a fully rhombic efg.
The orientations between the hyperfine and NQI tensor princip
al
axis systems and t
he g
-
matrix
reference frame are defined by the Euler angles (α, β, γ), with rotations performed within the zyz
convention where
α rotates xyz counterclockwise about
the
z
-
axis to give x'y'z', β rotates x'y'z
counterclockwise about
the
y'
-
axis to give x",y
",z", γ rotates xyz counterclockwise about
the
z"
-
axis to give
the
final frame orientation.
Electrochemistry
Room temperature cyclic voltammetry was performed in a nitrogen
-
filled glove box with a Gamry
Reference 600 potentiostat using a three
-
electrode
cell.
We used
a 3 mm diameter glassy carbon
working electrode
(CH Instruments)
, a 0.01 M Ag
+/0
in 0.1 M TBAPF
6
/
MeCN quasireference
electrode (Bioanalytical Systems, Inc.), and a platinum wire counter electrode (Kurt J. Lesker).
Potentiostatic electrochemical impedance spectra (PEIS) were recorded to obtain Nyquist plots to
determine the uncompensated resistance. 85
% of the uncompensated resistance was accounted for
using electronic compensation. 0.1
-
0.2 M TBAPF
6
was used as the electrolyte for all experiments.
Charge
-
discharge cycling experiments were performed in a 10 mL total volume H
-
cell in acetonitrile
with a N
afion 115 cation exchange membrane that had been soaked for 48 hours in 1.0 M TBAPF
6
in MeCN. Glassy carbon plates with
geometric
surface areas
of 1.3 cm
2
were used as current
collectors.
Spectroelectrochemistry
M
easurements were performed in
a nitrogen
-
filled glovebox with a quartz spectroelectrochemical
cell with a 0.17 mm path length from Pine Research Instrumentation (AKSTCKIT3), a
gold
honeycomb electrode
(Pine Instruments)
,
and a platinum
wire counter electrode
. Measurements
were recorded using an A
nalytical Instrument Systems, Inc. DT2000 deuterium
-
tungsten
UV
-
vis
-
NIR
light source coupled to Stellarnet Black Comet UV
-
vis and DWARF
-
Star NIR spectrometers
.