Novel photonic materials
Manthos G. Papadopoulos
Institute of Organic and Pharmaceutical Chemistry.
National Hellenic Research Foundation
48 Vas. Constantinou Av.
Athens 11635
We will consider a series of derivatives,
which have interesting
linear and nonlinear optical properties
and possible applications
in the photonic industry
Unifying features of this work:
•Molecules with large NLO properties
and how these can be interpreted
•Discovery of mechanisms in order
to modify the L&NLO properties
More specifically, we shall comment on the results
of three projects:
1. The L&NLO properties of derivatives
involving noble gas atoms
2. The L&NLO properties of [60]fullerene
derivatives
3. The structure and properties of Ni-dithiolenes
Definition of the electric properties
E = E(0) -μαFα - (1/2)ααβFαFβ - (1/6)βαβγFαFβFγ
- (1/24)γαβγδFαFβFγFδ - ...
μα : Dipole moment
ααβ: Polarizability
βαβγ: First hyperpolarizability
γαβγδ: Second hyperpolarizability
Why the L&NLO properties are important:
Theory
 Study of L&NLO processes (e.g. Kerr effect)
 Intermolecular interactions
Applications
 Design and study of NLO materials
(optical processing of information,
optical computing)
Noble gas derivatives
Definition of the project:
We consider insertion of a noble gas atom, Ng,
in the chemical bond A-B, leading to A-Ng-B.
Specific examples we will consider involve insertion of:
Ar in HF leading to HArF
Xe in HCnH leading to HXeCnH
Xe in AuF lading to AuXeF
Why are the noble gas derivatives
interesting and significant?
It is amazing what a noble gas atom, in the
middle of a single bond can do, for example it
leads to:
large NLO properties,
significant charge transfer etc
Which is the expanation?
HArF
A. Avramopoulos, H. Reis, J. Li and M. G. Papadopoulos,
J. Am. Chem. Soc., 126, 6179 (2004).

Properties of noble gases
 Synthesis of HArFa (argon fluoro-hydride)
[first covalent neutral cond. argon der.]
photolysis of HF in solid argon matrix
Point of interest:
The effect of Ar on the NLO
properties of the resulting derivative
a. L. Khriachtchev et al., Nature, 406, 874 (2000)
The dipole moment, polarizability and
first hyperpolarizability of HArF (in a.u.)
μz
αzz
βzzz
Pol
HF
MP2
CCSD(T)
3.139
2.691
2.578
37.61
55.37
59.80
-597.8
-1220.9
-1418.1
aug-cc-pV5Z
HF
MP2
3.085
2.653
37.80
54.01
-578.7
-1102.5
Rationalization of βzzz
(0) 
3( ee   gg )( ge ) 2
μgg: ground state dipole moment
μee: excited state dipole moment
μge: transition dipole moment
Εge: transition energy
(E ge ) 2
μgg: 3.473/0.745 a.u.
μee: -0.814/-0.907 a.u.
μge: 1.419/-0.611a.u.
Εge: 0.276/0.570 a.u.
Method: HF/Pol, CIS/Pol
Comparison of
HArF with HF
All the above properties contribute so that
βzzz of HArF is much larger than that of HF
Reliabity of TSM
HArF βzzz=-561.5 a.u. HF/Pol
-340.7 a.u. TSM
HF
βzzz=-7.4 a.u. HF/Pol
-5.7 a.u. TSM
Reliability of TSM
Large effect of Ar
HF…Ar van der Waals complex
μz=0.983 a.u. (3.473 a.u.)
αzz=19.11 a.u. (34.25 a.u.)
βzzz = -35.09 a.u. (-561.5 a.u.)
Charge of Ar: 0.02 (0.56)
Method: HF/Pol
ratio=16
ratio=28
Comparison of HArF with
C6H6
Αzz = 44.74 a.u. (34.25 a.u.)
Method: MP4[SDQ]
P-nitro-aniline
βzzz = 797.5 a.u. ( -561.5 a.u.)
Method: HF/Pol
The linear and nonlinear optical
properties of derivatives with inserted
Xe
The first Xe derivative was reported by Bartlet in
1962
[Proc. Chem. Soc., 218(1962)]
A large number of Xe compounds have been
reported since then
HXeF, AuXeF, XeAuF
F. Holka,A. Avramopoulos, O. Loboda, V. Kellö, M. G. Papadopoulos,
Chem. Phys. Letters, 472, 185 (2009)
Points of interest:
•Effect of Xe
•Comparison of H with Au
HXeF, AuXeF: not synthesized yet
XeAuF: several NgMF have been synthesized
Ng: Ar, Kr, Xe
M: Cu, Ag, Au
X: F, Cl, Br
Bonding:
Xe - Au bond: covalent [1]
Au - Xe [AuXeF] bond: partially covalent
(AXe)+ F- : significant charge transfer
A= H, Au
The barrier height
AuXeF: 119 kJmol-1
separates
the global minimum (AuF+Xe)
from the local minimum
1. S. A. Cook and M. C. L. Gerry, J. Am Chem. Soc. 126, 17000 (2004).
NBO charges
AuXeF
XeAuF
Xe
0.498
0.159
Au
0.377
0.650
F
-0.876
-0.810
Method: HF/aug-cc-pVQZ
Similar charges on F
Quite different charges for Xe of XeAuF and AuXeF
L&NLO properties
μz
αzz
βzzz
HXeF
2.019
59.7
-571
AuXeF
2.243
184.3
-2441
XeAuF
2.612
76.4
-265
Method: CCSD(T)
Basis set: aug-cc-pVQZ
ECP: Au(60), Xe(28)
The position of Xe has a great effect on αzz and βzzz
βzzz (AuXeF) / βzzz (AuF) = 6.0
βzzz (XeAuF) / βzzz (AuF) = 0.7
βzzz (HXeF) / βzzz (HF) = 57.0
Xe may greatly affect βzzz
Method: CCSD(T)
Basis set: aug-cc-pVQZ
Relativistic contribution:
AuXeF
NR
R
μz
3.675
2.047
αzz
211.52 188.06
βzzz -13520 -1826
Methods: CCSD(T), Douglas-Kroll
Basis sets: PolX, PolX_DK
βzzz = great effect of relativistic contribution
Novel compounds derived by
Xe inserted into HC2H and HC4H:
L&NLO properties
A.Avramopoulos, L. Serrano-Andres, J. Li, H. Reis and M. G. Papadopoulos,
J. Chem. Phys., 127, 214 (2007).
Preparation
HXeC2H and HXeC2XeH:
They are prepared in a low-temperature Xe matrix using UV
photolysis of C2H2 and subsequently annealing at 40-45K
[JACS, 125, 4696 (2003)]
HXeC4H:
Tanskanen et al. reported its preparation
[JACS, 125, 16361 (2003)]
HC2XeC2H:
Ansbacher et al. predicted that the diacetylide Xe exists
as a metastable chemically-bound compound
[PCCP, 8, 4175 (2006)]
Resonance structures of HXeC2H
Structures
Weight (%)a
H–Xe+C–CH (I)
44
H·Xe·CCH (II)
26
H–Xe+–CCH (III)
14
H–Xe2+C–CH (IV)
11
H+XeC–CH (V)
Method:CASVB(6,4)/3-21G*
5
Charge transfer in HXeC2H
Intra-molecular
Inter-molecular
NBO Charge Distribution
•1 and 2 Xe atoms:
Approx. the same
charge
•The chain length does
not appear to have an
effect
•1 Xe atom
End:0.79 e
Middle:1.02 e
Method:HF/aug-cc-pVZ
•3 Xe atoms:
The middle one has much larger
charge
Inter-molecular charge transfer
{Xe matrix}/HXeC2H
Two models
(a) 6 Xe atoms octahedrally placed around HXeC2H
A1A2=7.56 a.u.
A2A3=9.45 a.u.
Method:MP2/aug-cc-pVDZ
(b) 8 Xe atoms arranged in a cube
A1A2=15.12 a.u.
NBO analysis:
insignificant CT takes place from the Xe
environment to HXeC2H:
0.02e in the first model and
0.002e in the second model
HXeC2H
HC2H
The effect of
Xe
Is significant
Method:CCSD(T)/B1
HXeC2XeH
HXeC2H
The effect of
1 and 2
Xe atoms
Method: MP2/B1
H2C2H
The effect of Xe
in connection with effect
of the chain length
Δγzzzz = 30 000 au (approx.)
H2C4H
H2XeC2H
Δγzzzz = 340 000 au (approx.)
H2XeC4H
H-Xe-CC-CC-H
γzzzz =111 190 a.u
H-CC-Xe-CC-H
γzzzz =28 488 a.u.
H-CC-CC-H
γzzzz = 31 224 a.u.
Xe leads to a reduction of γzzzz !
The position of Xe has a significant effect on γzzzz
Method: MP2/aug-cc-pVDZ
Decomposition channels of HXeC2H
H+ Xe + C2H
34 kcalmol-1
HXeC2H
104 kcalmol-1
Xe + HC2H
The barrier to this exothermic reaction is very high, 64.6 kcalmol-1
and prevents the molecule from dissociation
T. Ansbacher et al., PCCP, 8, 4175 (2006)
Vibrational properties
Example: HXeC2H
αpvzz = [μ2](0,0) = 60.13 a.u
Vibrational Modes:
H-Xe: 1681cm-1
Xe-C: 313 cm-1
[μ2](0,0) = 13.1 a.u
[μ2](0,0) = 46.8 a.u
The other modes have a negligible contribution (0.23 a.u.)
Method:MP2/aug-cc-pVDZ
βpvzzz = [μα](0,0) = -835 a.u.
Vibrational Modes:
H-Xe: 1681cm-1
Xe-C: 313 cm-1
[μα](0,0) = 1212 a.u
[μα](0,0) = -2079 a.u
The other modes have a very small contribution
(32 a.u.)
Method:MP2/aug-cc-pVDZ
Local field effect
The Xe derivatives have been synthesized in a Xe matrix
Thus it would be useful to compute the effect of the Xe
environment on the L&NLO properties
Example: HXeC2H
The discrete local field approximation has been applied
Only the dipole and induced dipole interactions between
HXeC2H and the Xe environment are considered
Local field expression:
Fk  ( 0Vcell )
1
N

k ' k
(11)
kk ',
L
[  k   k ', Fk ' ]
,
Where
N is the number of molecules in the cell
Vcell is the volume of the cell
ε0 is the permitivity of vacuum
α,β,γ are the Cartesian components
Fk’α is the permanent local field effect on molecule k’ due to the surrounding molecules
μk’β is the dipole moment of the free molecule k’
αk’αβ is the polarizability of the free molecule k’
L(11) is the Lorentz-factor tensor
Model:
Cubic closed packed with dimensions a=b=c=24.8092 Å
It involves 255 Xe atoms
Y
H
Xe
C C
H
Z
X
Employed data:
HXeC2H: Dipole moment and polarizability of at the
CCSD(T) level and
Xe: experimental polarizability value (27.10 au)
Results:
Local field: Fz=-4.4x10-3 au
μz: 50.5%
αzz: 2.5%
βzzz: 20.2%
γzzzz: 12.7%
Changes of properties
Interpretation of the results
Insertion of Xe in HCnH leads to a large increase of γzzzz
For example:
γzzzz(HXeC2H)=38740 au γzzzz(HC2H)=3380 au
Ratio=11.5
Why?
Method: CASSCF/CASPT2
Basis set:ANO-RCC
Xe:7s6p4d2f1g
C:4s3p2d1f
H:3s2p1d
CASSSF(10,14)
The computations have shown that insertion of Xe leads to:
(a) Excited states of lower energy
(b) An electronic spectrum which is more dense in low lying
states
(c) Many non-zero contributions to the transition dipole moment
matrix
The SOS model
The NLO properties are:
proportional to products of TDM matrix elements and
inversely proportional to products of energy differences
Therefore an enhancement to NLO properties is expected
SOS computed properties
HC2H
αzz =
HXeC2H
11.07 au
γzzzz = 3473 au
αzz
=
26.51 au
γzzzz = 9102 au
The SOS model reflects the expected trend
On the electronic structure of H-Ng-Ng-F
(Ng=Ar, Kr, Xe) and the L&NLO properties
of HXe2F
A.Avramopoulos, L. Serrano-Andre, J.Li, M. G. Papadopoulos,
J. Chem. Theory Comput. 6, 3365 (2010).
Questions:
The diradical character of HNg2F
and the L&NLO properties
Methods:
CASVB, MS-CASPT2, CCSD(T)
Electronic ground state description
HArArF:
HΚrΚrF:
HΧeXeF:
38% σ2 + 56% σσ*
53% σ2 + 39% σσ*
58% σ2 + 35% σσ*
Increase of the closed shell character:
Xe > Kr > Ar
Method: MS-CASPT2/ANO
CASVB computations show:
The total weight of the resonance structures
with diradical character is approx.:
99% for HArArF
97% for HKrKrF
87% for HXeXeF
The singlet-triplet (3Σ+) gap (STG)
provides an indication for the diradical
character of the system:
STG
HAr2F 4.7 kcal/mol
HKr2F 14.7 kcal/mol
HXe2F 28.7 kcal/mol)
Wirz suggested that a diradical is a molecule with
STG which does not differ by much more than
≈ 2kcal/mol.
The expression “diradicaloid”
would then extend this range to ≈ 24 kcal/mol.
So, all the HNg2F are diradicaloids.
HF
HXeF
HXe2F
μz
0.703
1.975
3.788
αzz
6.19
59.59
420.4
βzzz
γzzzz x 10-3
-11.5
0.284
-582.1
22.7
-11040
-4000
Method: CCSD(T)/aug-cc-pVDZ
Stability, Electronic Structure
and L&NLO Properties of
HXeOXeF and FXeOXeF
A.Avramopoulos, J. Li, G. Frenking, M. G. Papadopoulos,
J. Phys. Chem. A, 115, 10226 (2011)
 HXeOXeF (FXeOXeF) results
from introduction of 2 Xe atoms
in HOF (FOF)
 We have shown that the novel derivatives
HXeOXeF and FXeOXeF
can be synthesized, because they are
protected by high energy barriers
VB orbitals of HXeOXeF
CASPT2/ANO
CCSD/aug-cc-pVDZ
MP2/aug-cc-pVDZ
Description of the ground state
HXeXeF
58.0% σ2 + 35% σσ*
HXeΟXeH 77.0% σ2 + 9% σσ*
FXeΟXeF 76.5% σ2 + 10% σσ*
Insertion of O increases
the closed character
E1 = 14.9
E2 = 25.5
E3 = 90.3
Units: kcal/mol
Dissociation paths of HXeOXeF calculated at
the CASPT2/ANO level.
E4 = 50.1 kcal/mol
E5 = 31.9 kcal/mol
E6 = 20.1 kcal/mol
Method: CASPT2/ANO
ZPE has been taken into account
Reactants and products were connected through
Intrinsic Reaction Coordinate (IRC) calculations
HOXeF is another novel derivative
HXeOXeF is a local minimum and is higher in energy
than several of its dissociation products:
E(HXeOXeF) – E(HOF + 2Xe) = 125.4 kcal/mol
E(HXeOXeF) – E(HO + F + 2Xe) = 85.2 kcal/mol
E(HXeOXeF) – E(OF + H + 2Xe) = 9.0 kcal/mol
HXeOXeF: Metastable
Dissociation paths of FXeOXeF calculated at
the CASPT2/ANO level
E1= 49.5 kcal/mol
E2= 40.5 kcal/mol
E3= 32.1 kcal/mol
E4 = 30.1 kcal/mol
E5 = 13.2 kcal/mol
E6 = 11.1 kcal/mol
Frenking et al. [1] found that HArArF and HKrKrF
are associated with low-energy barriers.
Thus, they can NOT be observed.
But,
HXeXeF 13.1 kcal/mol
HXeOXeF 14.9 kcal/mol
FXeOXeF 40.5 kcal/mol
Thus O and F increase the barrier
and thus
FArOArF and FKrOKrF
may be observed.
G. Frenking et al., Angew. Chem. Int. Edition,
48, 366 (2009).
L&NLO Properties
HXeXeFa
HXeOXeF
HXeOXeH
FXeOXeF
μz
3.788
2.747
0.987
0.623
αzz
420.4
92.8
107.3
90.5
βzzz
-11040
-1720
-49
-89.0
Method: CCD(T)/aug-cc-pVTZ
a. aug-cc-pVDZ
Insertion of O reduces
the L&NLO properties
The L&NLO properties of some
Ni-Dithiolene derivatives
Luis Serrano-Andrés, A. Avramopoulos, J. Li, P. Labéquerie, D. Begué,
V. Kellö, M. G. Papadopoulos, J. Chem Phys., 131, 134312 (2009).
Points of interest:
• The low-lying excited states of NiBDT
• The impressive NLO properties and their
interpretation
Excited states structure of Ni(S2C2H2)2
State
ΔE/eV
Main configuration
11Ag ( diradicaloid)a
−0.004b
… (π2)2(π3)0 - (π2)0(π3)2
11B1u (pp*)c
0.000b
… (π2)1 (π3)1
.
.
.
14 states
31B3u (σSNi π π * π *)
3.064
… (σSNi)1 (π 1)1 (π 2)2 (π 3)2
13B1u (diradical)d
0.612
… (π 2)1 (π 3)1
11Ag [71% (p2)2(p3)0−21% (p2)0(p3)2].
b The energy difference is within the method accuracy. For simplicity
the 11Ag state will be considered the ground state at this level.
c 11B state 65% [(π )1(π )1].
1u
2
3
d 13B state 92% [(π )1(π )1].
1u
2
3
a
Basis set: ANO-RCC
Method: CASSCF/CASPT2
Remarks:
The main findings of the
CASSCF/CASPT2 computations are:
The quasidegenaracy of 11Ag and
11B1u and the large number of low
lying excited states.
These features are very likely to
lead to large NLO properties
Properties of Ni(S2C2H2)2
Property
Basis set
αzz
γzzzzx10-4
6-311G*
222.0
68.1
SDD[Ni]/631G*
221.9
55.8
ZPolX
245.3
67.7
aug-cc-pVDZ
244.7
71.9
aug-cc-pVTZ
245.2
68.0
aug-cc-pVQZ
245.4
67.6
Method: UBHandHLYP
Property
αzz
γzzzzx10-4
Method
UBHandHLYP
245.3
67.7
UCCSD
300.5
72.4
UCCSD(T)
364.3
119.0
CASSCF/CASPT2
m/a1b1b2a2b
12/4242 (4s2p,4s*2p*)
67.9/282.2
1647.5/216.0
16/4444 (4s4p,4s*4p*)
243.2/340.7
1102.7/184.7
20/4646 (4s6p,4s*6p*)
309.3/363.8
869.5/153.1
a
b
The properties were computed numerically. Base field: 0.005 au.
m: Number of active electrons; a1b1b2a2: Number of orbitals
in subspaces of C2v symmetry.
Basis set: ZPolX
Method: UBHandHLYP/
6-31G*
Main points
The big second hyperpolarizability of NiBDT
has been interpreted in terms of the
quasidegeneracy of the 11Ag and 11B1u states.
As well as the many low lying excited states.
The considered Ni-dithiolene derivatives have
very big NLO properties.
The L&NLO properties of [60]fullerene
derivatives
Points of interest:
Selection of the appropriate method (e.g. functional)
Computation of the electronic and vibrational contributions
Selection of functional groups
O. Loboda, R. Zalesny, A. Avramopoulos, J. –M. Luis, B. Kirtman, N. Tagmatarchis, H. Reis and
M. G. Papadopoulos, J. Phys. Chem. A, 113, 1159 (2009).
Overshooting
Effect:
3-55 larger
Ratio:
2
Comment: The substituents were selected according to increasing
Hammett σp constant, which may be used as a measure
of their electron donating capabilities.
Methods: BLYP and HF(it does not have the overshoot problem).
Ratio:
41
Remark:The ratio of the BLYP and the HF values increases monotonically and becomes
quite large for the strongest donors.
Concluding remarks
 Mechanisms which lead to large NLO properties
have been discussed
 Novel derivatives with possible photonic
applications have been proposed
Acknowledgement
Colleagues who contributed to this work:
Dr Aggelos Avramopoulos, NHRF, Greece
Dr Heribert Reis, NHRF, Greece
Dr Luis Serrano Andrés, Universitat de València, Spain
Dr Jiabo Li, SciNet Technologies, USA
Dr Robert Zalesny, NHRF, Greece
Dr Oleksandr Loboda, NHRF, Greece
Professor B. Kirtman, University of California, USA
Dr Josep Maria Luis, University of Girona, Spain
Dr Nikos Tagmatarchis, NHRF, Greece
Professor Vladimir Kellö, Comenius University, Slovakia