Synthesis,measurements,and theoretical analysis of carbazole derivatives祝国庆
with high-triplet-energy
Jianli Li a,Xiaoyun Mi a,Yuchun Wan a,Zhenjun Si a,b,n,Haiying Sun a,Qian Duan a,
Xingquan He c,Dong Yan a,Sha Wan a
a School of Materials Science and Engineering,Changchun University of Science and Technology,Changchun130022,PR China
b Institute of Organi
c Chemistry&Biochemistry,Czech Academy of Science,Praha616610,Czech Republic
c School of Chemistry&Environmental Engineering,Changchun University of Science an
d Technology,Changchun130022,PR China
a r t i c l e i n f o
Article history:
Received24September2011
Received in revid form
11December2011
Accepted21December2011
Available online31December2011
Keywords:
Synthesis
Crystal structure
Carbazole
Phosphorescence
Theoretical analys
a b s t r a c t
In order to obtain the blue light-emitting organic materials with high triplet state energy,two
3,5-diphenyl-4H-1,2,4-triazole(Tz)containing carbazole(Cz)derivatives of9-(4-(3,5-diphenyl-4H-
1,2,4-triazol-4-yl)phenyl)-9H-carbazole(TzCz1)and3,6-di-tert-butyl-9-(4-(3,5-diphenyl-4H-1,2,
4-triazol-4-yl)phenyl)-9H-carbazole(TzCz2)are synthesized using Cz acting as the starting material,
as well as characterized by the1H NMR spectra,ultraviolet–visible(UV–vis)absorption spectra,and the
IR absorption spectra.The luminescence quantum yields(LQYs)of TzCz1and TzCz2are measured in
CH2Cl2solution to be32.1%and47.5%,respectively.The electrochemical analysis and the photophysical
福利待遇
measurements suggest that the triplet energy levels and the energy gaps of the highest-occupied orbital
and the lowest-unoccupied orbital are2.83eV and3.59eV for TzCz1,and2.80eV and3.43eV for
TzCz2.At last,the theoretical analys of their ground state geometries and the simulated UV–vis
absorption spectra are carried out at B3LYP1/6-31G*level.The studies mentioned above indicate that
both TzCz1and TzCz2are suitable for the host materials of blue light-emitting diodes.
&2012Elvier B.V.All rights rerved.
1.Introduction
Currently,the synthesis of the carbazole(Cz)bad com-
pounds[1]and the studies on their properties[2,3]greatly appeal
to the rearchers becau they can be applied in many areas
[4–7]including medicament and anticorrosion.For example,
Wang ported that the Cz alkaloids,glybomine B and
glycoborinine,demonstrated anti-HIV activity with an IC50of
9.73mg/mL and4.47mg/mL,respectively[4].Gopia et al.also
reported that the N-vinyl Cz had a good corrosion inhibiting
character[5].At the same time,the application of the Cz and its
derivatives[8–10]in optoelectronic devices becomes another hot
topic,becau the materials have large triplet energy gap,
which is especially important for the improvement of the perfor-
mance of the blue phosphorescent organic light-emitting diodes
(PhOLEDs)[11,12]by efficiently preventing the back excitation
transfer from the guest materials to the host materials.As a result,
more and more host materials bad on Cz were synthesized for
the blue PhOLEDs[13–23],for example,Cho and Lee[7]and
Lee et al.[20]reported the blue PhOLEDs bad on TSPC and
mCPPO1posss the maximum external quantum efficiencies of
22.0%and25.1%,respectively.
In2007,Kim et al.[15]synthesized a ries of Tz derivatized
groups containing Cz compounds and found that3,5-diphenyl-4H-
1,2,4-triazole(Tz)posss the electron transporting character-
istic,which is helpful to balance the injection and transport of the
charge carrier in OLEDs.Therefore,in this article,we report
the synthesis and the properties of Tz group containing Cz
compounds of9-(4-(3,5-diphenyl-4H-1,2,4-triazol-4-yl)phenyl)-
含饴弄孙的意思9H-carbazole(TzCz1)and3,6-di-tert-butyl-9-(4-(3,5-diphenyl-
4H-1,2,4-triazol-4-yl)phenyl)-9H-carbazole(TzCz2),where TzCz1
is a known compound[24],but its crystal structure,electroche-
mical properties,and the corresponding theoretical analys were
not systematically studied.
2.Experimental ction
2.1.Measurement
The IR spectra were acquired using a FTIR-8400S SHIMADZU
spectrophotometer in the4000–400cmÀ1region with KBr pel-
lets.Element analys were performed using a Vario Element
Analyzer.1H NMR spectra were obtained using a Bruker AVANVE
Contents lists available at SciVer ScienceDirect
journal homepage:/locate/jlumin
Journal of Luminescence
0022-2313/$-e front matter&2012Elvier B.V.All rights rerved.
doi:10.1016/j.jlumin.2011.12.062
n Corresponding author at:School of Materials Science and Engineering,
冬天诗
Changchun University of Science and Technology,Changchun130022,PR China.
Tel.:þ8643185583019;fax:þ8643185583015.
E-mail address:szj@cust.edu(Z.Si).
Journal of Luminescence132(2012)1200–1206
400MHz spectrometer with tetramethylsilane as the internal standard.The Ultraviolet–visible(UV–vis)absorption and photo-luminescent spectra of CH2Cl2solutions with ca.10À4mol/L samples were recorded on a Perkin Elmer Lambda900UV/Vis/ NIR spectrophotometer and a SPEX Fluorolog3spectrometer, respectively.The phosphorescent spectra were measured on Hitachi Spectrophotometer model F-4500at77K.The lumines-cence quantum yields(LQYs)were measured by comparing fluorescence intensities(integrated areas)of a standard sample (quinine sulfate)and the unknown sample according to the following equation:
F unk¼F stdðI unk=A unkÞðA std=I stdÞðZ
unk
=Z stdÞ2ð1Þwhere F unk is the LQY of the unknown sample;F std is the LQY of quinine sulfate and taken as0.546[25];I unk and I std are the integratedfluorescence intensities of the unknown sample and quinine sulfate at corresponding excitation wavelength,respec-tively;A unk and A std are the absorbances of the unknown sample and quinine sulfate at the corresponding excitation wavelengths, respectively.The Z unk and Z std are the refractive indices of the corresponding solvents(pure solvents were assumed).
The crystals of[TzCz1H]ClÁ2CHCl3were cultured in CHCl3 solution before the product was washed in NaHCO3aqueous solution and measured on a Bruker Smart Apex CCD single-crystal diffractometer using l(Mo K a)radiation,0.7107˚A at293K.The structure was solved using the SHELXL-97program[16–28].The crystallographic refinement parameters of[TzCz1H]ClÁ2CHCl3are summarized in Table1,and the lected bond distances and angles of TzCz1are given in Table2.
Cyclic voltammetry measurements were conducted on a YHMEC-3000voltammetric analyzer with a polished Pt plate as the working electrode,Pt mesh as the counter electrode,and a commercially avai
lable saturated calomel electrode(SCE)as the reference electrode,at a scan rate of0.1V/s.The voltammograms were recorded using CH3CN solutions with$10À3M sample and 0.1M tetrabutylammonium hexafluorophosphate(TBAPF6)as the supporting electrolyte.Prior to each electrochemical measure-ment,the solution was purged with nitrogen for$10–15min to remove the dissolved O2gas.The energy level of the highest-occupied molecular orbital(E HOMO)and the lowest-unoccupied molecular orbital(E LUMO)was calculated according to Ref.[29] and listed in Table3.
2.2.Preparation of the materials
N,N-Dimethylacetamide(DMAc),N,N-dimethylaniline,and toluene were dried with standard procedure[30]and stored under N2,other chemicals are commercially available and ud without further purification.9-(4-nitrophenyl)-9H-carbazole (A1),3,6-di-tert-butyl-9-(4-nitrophenyl)-9H-carbazole(A2)[31], 4-(9H-carbazol-9-yl)aniline(B1),4-(3,6-di-tert-butyl-9H-carba-zol-9-yl)aniline(B2)[32],and N0-(chloro(phenyl)methylene)ben-zohydrazonoyl chloride(C)[33]were synthesized according to the reported methods.All reactions and manipulations were carried out under N2with the u of Schlenk techniques.Solvents ud in luminescent and electrochemical studies were of spectro-scopic and anhydrous grades,respectively.
2.2.1.Synthesis of TzCz1
The mixture of compound B1(0.516g,0.2mmol),compound C (0.544g,0.2mmol),and10mL of N,N-dimethylaniline was stir-red at1351C for12h under N2atmosphere.After adding aqueous solution of HCl(30mL,2N),the mixture was stirred for an additional30min.The precipitated solid was collected byfiltra-tion,washed in NaHCO3aqueous solution,dried in vacuo,and recrystallized from EtOH to afford TzCz1(60%);1H NMR(CDCl3): 7.321–7.368(m,2H),7.393(d,2H,J¼3),7.424(d,4H,J¼8), 7.452–7.492(m,4H),7.561(d,2H,J¼8),7.591–7.621(m,4H), 7.698(d,2H,J¼4),8.156(d,2H,J¼8).IR(KBr)/cmÀ1:3066,2356, 1514,1454,1234.Anal.Calcd.for C32H22N4:C,83.09;H,4.79;N, 12.11.Found:C,83.20;H, 4.52;N,12.41.UV–vis:292nm, 323nm,338nm.
2.2.2.Synthesis of TzCz2
TzCz2was prepared by an analogous procedures ud in the preparation of TzCz1with a yield of54%1H NMR(CDCl3):1.471(s 18H),7.342(d,2H,J¼8),7.441–7.461(m,4H),7.495–7.522(m, 4H),7.559–7.606(m,2H),7.660(d,4H,J¼8),7.734(d,2H,J¼8), 8.145(d,2H,J¼1.6).IR(KBr)/cmÀ1:3055,2956,2943,2378, 2320,1517,1471.Anal.Calcd.for C40H38N4:C,83.59;H,6.66;N, 9.75.Found:C,83.72;H,6.49;N,9.86.UV–vis:296nm,332nm, 344nm.
Table1
Crystal data and structure refinement for[TzCz1H]þClÀ(CHCl3)2
[TzCz1H]þClÀ(CHCl3)2
Formula C34H25Cl7N4
FW737.73
T(K)293(2)K
Wavelength(˚A)0.71073
Cryst.syst.Orthorhombic
Space group Pbca
a(˚A)10.2061(5)
b(˚A)15.9437(7)
c(˚A)42.5960(18)
a(deg.)90
b(deg.)90
g(deg.)90
V(˚A3)6931.3(5)
Z28
偷影子的人
r calc.(Mg/m3) 4.949
m(mmÀ1) 2.113
F(000)(e)10528
Range for collection(deg.)0.96–25.04
Reflections collected33662
Completeness99.9%(y¼25.04)
Data/restraints/parameters6123/0/406
Goodness-of-fit on F20.985
R1,wR2[I42s(I)]0.0716/0.1697
R1,wR2(all data)0.1273/0.2053Table2
Bond lengths[˚A]and angles[deg.]for[TzCz1H]þClÀ(CHCl3)2
C(19)–C(20) 1.467(6)C(19)–N(2) 1.382(6) C(26)–C(27) 1.471(6)C(26)–N(2) 1.358(5) C(1)–N(1) 1.396(6)C(19)–N(3) 1.306(6) C(12)–N(1) 1.402(6)N(3)–N(4) 1.367(5) C(13)–N(1) 1.423(6)N(4)–H(4)0.86
C(16)–N(2) 1.444(5)C(26)–N(4) 1.307(6)
C(2)–C(1)–N(1)129.8(4)N(4)–C(26)–C(27)125.4(4) N(1)–C(1)–C(6)108.7(4)N(2)–C(26)–C(27)128.8(4) C(11)–C(12)–N(1)129.6(5)C(1)–N(1)–C(12)108.8(4) N(1)–C(12)–C(7)108.4(4)C(1)–N(
1)–C(13)125.1(4) C(18)–C(13)–N(1)120.0(4)C(12)–N(1)–C(13)125.5(4) C(14)–C(13)–N(1)119.3(4)C(26)–N(2)–C(19)106.5(4) C(15)–C(16)–N(2)117.8(4)C(26)–N(2)–C(16)127.2(4) C(17)–C(16)–N(2)119.7(4)C(19)–N(2)–C(16)126.3(4) N(3)–C(19)–N(2)110.7(4)C(19)–N(3)–N(4)104.0(4) N(3)–C(19)–C(20)124.5(4)C(26)–N(4)–N(3)113.0(4) N(2)–C(19)–C(20)124.8(4)C(26)–N(4)–H(4)123.5
N(4)–C(26)–N(2)105.8(4)N(3)–N(4)–H(4)123.5
J.Li et al./Journal of Luminescence132(2012)1200–12061201
2.3.Computational details
The geometrical structures of the ground states were opti-mized in gas pha by the density functional theory (DFT)[34]with an B3LYP1exchange-correlation functional calculus (a hybrid method combining five functionals,Becke þSlater þHF exchange,and LYP þVWN1correlation)[35,36].On the basis of the optimized ground state geometry structures,the UV–vis absorption spectral properties in CH 2Cl 2media were calculated by time-dependent DFT (TDDFT)[37],associating with the polar-ized continuum model (PCM).The 6-31G n [38,39]basis t on C,H,N atoms was employed for both TzCz1and TzCz2to ensure that the calculations are performed on the same level.The calculated ele
ctronic density plots for frontier molecular orbitals were prepared using the wxMacMolPlt-7.4.2software.All the calculations were performed with the Firefly QC package [40],which is partially bad on the GAMESS (US)source code [41].
3.Results and discussion 3.1.Structural characterization
As prented in Scheme 1,the precursor of B1(B2)is prepared from the copper-catalyzed Ullmann reactions between 1-iodo-4-nitrobenzene and Cz (3,6-di-tert-butyl-9H-carbazole,Cz2),which is reduced by the reducing agent of NH 2NH 2ÁH 2O(85%)-Pd (5%)/carbon in EtOH under N 2protection.Meanwhile,the compound C
is synthesized according to the method in literature.At last,the reaction between B1(B2)and C gives the target compounds of TzCz1(TzCz2).The purity and composition of TzCz1and TzCz2are confirmed by 1H NMR,IR,and elemental analys.At the same time,the colorless needle crystals of [TzCz1H]Cl Á2CHCl 3are cultured from its chloroform solution,and the solid evidence to support the structure of TzCz1is obtained using the single-crystal X-ray diffraction method.An ORTEP diagram of TzCz1is shown in Fig.1.The crystal data and the lected structural data for [TzCz1H]Cl Á2CHCl 3are prented in Tables 1and 2,respectively.
The distances of C(13)–N(1)and C(16)–N(2)are 1.423(6)˚A
and 1.444(5)˚A,respectively,and the dihedral angles of C(12)–N(1)–
C(13)–C(14)and C(17)–C(16)–N(2)–N(26)are 56.841and 67.011,respectively.The differences should be attributed to the fact that the phenyl groups on 3,5-position of Tz moiety lead to the bigger steric hindrance.At the same time,the existence of the hydrogen ion on the N(4)makes the distance of C(26)–C(27)
(1.471(6)˚A)
to be longer than that of C(19)–C(20)(1.467(6)˚A).But according to the contribution of Cl À
,the dihedral angles of C(28)–C(27)–C(26)–N(4)(26.031)are much smaller than tho of C(21)–C(20)–C(19)–N(3)(43.501).3.2.Electrochemistry
The electrochemical properties of TzCz1and TzCz2are studied in CH 3CN solution through cyclic voltammetry using TBAPF 6as the supporting electrolyte (Fig.2).During the anodic scan,the irreversible anodic waves peaked at þ1.52V with an ont
Table 3
Electrochemical and photophysical parameters of TzCz1and TzCz2.Complex
Absorption l (nm)a
Excitation l (nm)a
Emission
E HOMO (eV)
E LUMO (eV)
l (nm)a
f (%)
l (nm)b
E T (eV)TzCz1255,292,324,339290,316,327,339345,35955.66438 2.83À5.84À2.25TzCz2
261,296,311,344293,307,336,345353,369
60.76
443
2.80
知否知否应是绿肥红瘦结局À5.88
À2.45
a The spectra are measured at room temperature.b
The spectra are measured at 77
K.
Scheme 1.Synthesis route to TzCz1and TzCz2.(i)1-iodo-4-nitrobenzene,DMAc,1701C,24h;(ii)NH 2NH 2ÁH 2O (85%),Pd (5%)/C,EtOH,reflux,10h;(iii)N,N-dimethylaniline,B1or B2,1351C,12h.
J.Li et al./Journal of Luminescence 132(2012)1200–1206
1202
oxidation potential(V ont(OX))ofþ1.10V for TzCz1andþ1.25V with a V ont(OX)ofþ1.14V for TzCz2.As can be en from the ints of Fig.2,the current prent somewhat increas when the oxidation potential is gradually shifting to lower potentials during repeated cyclic voltammetry scans.As revealed in the literature,it is important to block the active sites of Cz derivatives when the compounds transport positive charge carriers in PhOLEDs[42]. The values of the E HOMO are obtained according to the following equation:E HOMO¼[V SCEÀV ont(OX)]eV[43],where V SCE is the electrode potential of the SCE,which should beÀ4.74eV in a vacuum,and the values of E HOMO for TzCz1and TzCz2are calculated to beÀ5.84eV andÀ5.88eV,respectively.According to the previous reports,the E HOMO of mCP isÀ5.91eV[6],being lower than tho of TzCz1and TzCz2,which reveals that the introduction of the Tz moiety in p-positions of the phenyl unit should lead to the reduction of the hole injection barrier,thereby facilitating the injection of positive charge ca
rriers.At the same time,the values of E LUMO for TzCz1and TzCz2are obtained according to the following equation:E HOMO¼[E LUMOÀ1240/ l(Abs)]eV,where l(Abs)prents the longest absorption wave-length(345nm for TzCz1and362nm for TzCz2),which can be obtained from the corresponding UV–vis absorption spectra (Fig.3).Therefore,the values of E LUMO are calculated to be À2.25eV for TzCz1andÀ2.45eV for TzCz2,and the energy gaps of TzCz1and TzCz2should be3.59eV and3.43eV,respectively.
3.3.Photophysical properties
The UV–vis absorption spectra of TzCz1and TzCz2in CH2Cl2 are prented in Fig.3,and the lected data of the UV–vis absorption spectra are listed in Table3.As can be en from Fig.3, the absorption bands of TzCz1and TzCz2in the range of 300–360nm should be assigned to the ICT transitions bad on p(Cz)-p n(TzþPh),and the bands with the wavelength being shorter than300nm should be contributed by the mixture of the p(Tz)-p n(Tz)/p(Cz)-p n(Cz)transitions[44].The
assignments
Fig.1.ORTEP drawing of a crystal of TzCz1with displacement ellipsoids at the
50%probability level.Two CHCl3solvent molecules and a ClÀanion is prent per
unit cell and have been omitted,along with all hydrogen atoms,for
clarity.
Fig.2.Cyclic voltammograms of complexes TzCz1(a)and TzCz2(b)measured in CH3CN(vs.SCE)at a scan rate of0.1V/s.A polished Pt plate and a Pt mesh were ud as the working electrode and the counter electrode,respectively.TBAPF6was taken as supporting
electrolyte.
Fig.3.UV–vis absorption spectra and excitation spectra of TzCz1and TzCz2in
dilute CH2Cl2,along with the UV–vis absorption spectra of Cz,Cz2,and TzMe.
J.Li et al./Journal of Luminescence132(2012)1200–12061203
are bad on the absorption spectra of Cz,Cz2,and 3,5-diphenyl-4-(p -tolyl)-4H-1,2,4-triazole (TzMe)prented in Fig.3and the theoretical studies (vide infra).
The PL spectra of TzCz1and TzCz2in CH 2Cl 2solution are prented in Fig.4.Upon UV excitation,the PL spectra of TzCz1and TzCz2prent their vibronic structure with the maximum emission band centered at 359nm and 369nm,respectively.Due to the steric effect and the electron donor property of the tert -butyl groups in TzCz2,the emission band of TzCz2is prent at longer wavelength than that of TzCz1,and the LQY of TzCz2(47.5%)is almost 1.5times higher than that of TzCz1(32.1%)in dilute CH 2Cl 2solution.The phosphorescent spectra of TzCz1and TzCz2measured in EtOH at 77K are prented in the int of Fig.4.It is found that the highest energy phosphorescent band peaked at 438nm for TzCz1and 443nm for TzCz2and the triplet energy levels are calculated to
be 2.83eV for TzCz1and 2.80eV for TzCz2,which are higher than tho of the commonly ud triplet blue-emitters FIrpic (2.62eV)and FIr6(2.72eV)[45,46].Therefore,TzCz1and TzCz2can be potentially ud as the host materials of the blue PhOLEDs.3.4.Theoretical analysis
3.4.1.Frontier molecular orbital properties
The lective parameters of the optimized molecular struc-tures of TzCz1and TzCz2are collected in Table 4.As can be en from Table 4,The bond distance of C(21)–N(24)of TzCz2is
simulated to be 1.41˚A,
which is 0.01˚A shorter than that of TzCz1(1.41˚A).
The bond angles simulated for TzCz2slightly depart from tho of TzCz1,which should be attributed to the appearance of the tert -butyl groups in TzCz2.According to the simulated molecular structure of TzCz1,the distances of Cz moiety and Tz
moiety to the phenylene group are calculated to be 1.42˚A
and 1.43˚A,
respectively,and the dihedral angles of C(22)–C(21)–N(24)–C(28)and C(7)–N(11)–C(18)–C(19)are 52.971and 67.391,respectively.Meanwhile the dihedral angle of C(17)–C(12)–C(10)–N(11)and the bond distance of C(12)–C(10)are 33.051
and 1.47˚A,
respectively,which are almost equal to the dihedral angle of C(67)–C(6)–C(7)–N(11)of 33.101and the bond distance
of C(7)–C(5)of 1.47˚A.
The results are obviously different to tho from the experimental measurements,which should be attributed to the fact that the effect of the H þion and the Cl Àcation on the Tz moiety are ignored during the theoretical studies of the ground state geometry of TzCz1,along with the fact that
the theoretical studies are optimized in the gas pha and the experimental measurements are in a tight crystal lattice [47].Table 5prents the compositions of the calculated frontier molecular orbitals of TzCz1and TzCz2and the electron density plots of the HOMO and the LUMO of TzCz1and TzCz2are shown in Fig.5.The HOMOs of TzCz1and TzCz2are compod of the p orbitals localized o
n Cz moiety with Z 85.5%contributions,the HOMO À1of TzCz1is compod of the p orbitals localized on Tz moiety with 99.5%contributions.The HOMO À2of TzCz1and HOMO À1and HOMO À4of TzCz2are compod of the p orbitals localized on Cz moiety with Z 96.0%contributions.Meanwhile,the HOMO À2of TzCz2,the HOMO À3s of TzCz1and TzCz2,and the HOMO À4of TzCz1are contributed by the p orbitals localized on Tz moiety with Z 88.6%distributions.
The LUMO of TzCz1is mainly compod of the p n orbitals localized on Tz with 46.6%contributions and Ph moieties with 46.1%contributions.Similar to the LUMO of TzCz1,the LUMO of TzCz2and the LUMO þ2s of TzCz1and TzCz2are also compod of the p n orbitals localized on Tz with 448.5%contributions and Ph moieties with 438.1%contributions.The LUMO þ1s of TzCz1and TzCz2are compod of the p n (Ph)orbitals with 479.2%contributions.The LUMO þ3s of TzCz1and TzCz2are mainly compod of the p n orbitals localized on Cz moiety with 492.0%contributions.Meanwhile,the LUMO þ4are mainly compod of the p n orbitals localized on the Tz moiety with 94.0%contribu-tions for TzCz1and 93.5%contributions for TzCz2.As prented in Table 5,the E HOMO s and the E LUMO s are calculated to be À5.64eV and À1.23eV for TzCz1and À5.44eV and À1.18eV for TzCz2,respectively.Therefore,the energy gaps of the HOMO and the LUMO are simulated to be 4.41eV for TzCz1and 4.26eV for TzCz2,which are bigger than tho from the experimental measurements.The difference of the orbital energy between
the
Fig.4.PL spectra of TzCz1and TzCz2in CH 2Cl 2at room temperature.Int:the PL spectra of TzCz1and TzCz2measured in MeOH air at 77K.
Table 4
Bond lengths [˚A]
and angles [deg.]for simulated TzCz1and TzCz2.TzCz1
TzCz2C(5)–C(7)
1.47 1.47C(10)–C(12) 1.47 1.47C(7)–N(8) 1.32 1.32C(10)–N(9) 1.32 1.32N(8)–N(9) 1.37 1.37C(7)–N(11) 1.39 1.39C(10)–N(11) 1.39 1.39C(18)–N(11) 1.43 1.43C(21)–N(24) 1.42 1.41C(28)–N(24) 1.40 1.40C(25)–N(24) 1.40 1.40C(5)–C(7)–N(8)123.27123.27C(5)–C(7)–N(11)127.36127.35C(7)–N(8)–N(9)108.36108.35N(11)–C(7)–N(8)109.37109.38N(8)–N(9)–C(10)108.35108.35N(9)–C(10)–N(11)109.37109.38C(10)–N(11)–C(7)104.54104.54N(9)–C(10)–N(12)123.27123.29N(11)–C(10)–C(12)127.36127.33C(7)–N(11)–C(18)127.73127.70C(10)–N(11)–C(18)127.73127.75C(19)–C(18)–N(11)119.96119.95C(23)–C(18)–N(11)119.96119.98C(20)–C(21)–N
(24)120.28120.26C(22)–C(21)–N(24)120.28120.33C(21)–N(24)–C(28)125.81126.03C(21)–N(24)–C(25)125.81125.84N(24)–C(28)–C(36)129.52130.09N(24)–C(25)–C(29)129.52130.22N(24)–C(28)–C(27)108.86109.12C(28)–N(24)–C(25)108.37108.12N(24)–C(25)–C(26)
108.86
108.97
J.Li et al./Journal of Luminescence 132(2012)1200–1206
小公司薪酬方案1204
experimental measurements and the theoretical calculations should be mainly attributed to the ignorance of the solution effect during the molecular structure optimization.
3.4.2.Simulation of the UV–vis absorption spectra
The curves of the theoretically simulated UV–vis absorption spectra of TzCz1and TzCz2prented in Fig.6are nicely fitted to tho from the experimental measurements.Similar to the experimental measurements,the simulated UV–vis absorption of TzCz2prents obvious red-shift in accordance w
ith that of TzCz1.This should be assigned to the fact that the energy gap between the HOMO and LUMO of TzCz2is much narrower than that of TzCz1(Tables 3and 5).As prented in Table 6,the lowest lying singlet -singlet absorptions of TzCz1and TzCz2contrib-uted by the configurations of HOMO -LUMO are calculated at 323and 349nm,respectively.According to the simulated com-position of the HOMO and LUMO (Table 5),the lowest lying transition for both TzCz1and TzCz2should be described as the ICT bad on the p (Cz)-p n (Tz þPh)transitions.
The absorption with the largest oscillator strength at 283nm and 242nm are in agreement with the experimental values of 282nm for TzCz1and 248nm for TzCz2.According to the fact that LUMO þ7of TzCz2is compod of the p n orbital on Cz moiety with ca.97.0%contribution and the other orbital information prented in Table 5,the dominant character of the higher energy absorptions are tentatively assigned to the ICT bad on [p (Cz)-p n (Tz þPh)]transitions for TzCz1and the [p (Cz)-p n (Cz)]transitions for TzCz2.At the same time,the absorptions with the moderate oscillator of both TzCz1and TzCz2are calculated to be the mixture transitions of the ICT and the p -p n transfer.
4.Conclusions
In summary,we synthesize two Cz derivatives of TzCz1and TzCz2,which are fully characterized by th
e 1H NMR,UV–vis absorption spectra,and the IR absorption spectra.It is found that the prence of tert -butyl groups leads to the relatively higher LQY and the lower energy gap of TzCz2.The triplet energy levels,which are deducted from the phosphorescent spectra,are only 2.83eV for TzCz1and 2.80eV for TzCz2.Both of the experimental studies and the theoretical analys suggest that TzCz1and TzCz2should posss the potential application as the host materials in blue
PhOLEDs.
Fig.5.Electron density plots of the frontier molecular orbital of TzCz1and TzCz2in gas pha at B3LYP1/6-31G n
level.
Fig.6.Simulated UV–vis absorption spectra of TzCz1and TzCz2in CH 2Cl 2media at B3LYP1/6-31G n level.
Table 5
Frontier molecular orbital compositions (%)of TzCz1and TzCz2calculated in the gas pha at the DFT/B3LYP1/6-31G n level.Orbital
TzCz1TzCz2E (eV)
Bond type
Distribution (%)E (eV)
Bond type
Distribution (%)Tz
Ph
Cz
Tz
Ph
Cz
LUMO þ4À0.48p n (Tz)94.0
À0.45p n (Tz)93.5
LUMO þ3À0.92p n (Cz)
92.0
À0.85p n (Cz)
97.1
LUMO þ2À0.94p n (Tz þPh)50.938.1-0.88p n (Tz þPh)48.544.2LUMO þ1À0.99p n (Ph)
80.4À0.93p n (Ph)
79.2LUMO
À1.23p n (Tz þPh)46.6
46.1
À1.18p n (Tz þPh)53.0
40.2
Energy gap 4.41 4.26HOMO À5.64p (Cz)85.5
À5.44p (Cz)87.3HOMO À1À5.95p (Tz)99.5
À5.85p (Cz)99.1
HOMO À2À5.99p (Cz)99.4
À5.93p (Tz)99.5HOMO À3À6.67p (Tz)93.6À6.63p (Tz)92.2
HOMO À4
À6.93
p (Tz)一个女孩的故事
88.6
À6.77p (Cz)
96.0
J.Li et al./Journal of Luminescence 132(2012)1200–12061205
