Photo-induced HTP and rotational motion switching from naphthopyran derivative

Yuna Kim

2015.07.21

Laboratory of smart molecules, Research Institute for Electronic Science, Hokkaido University

Work progress report

Cholesteric liquid

crystalline molecule

Cholesteric phase; selectively reflecting incident white light

Applications; Displays, polarizers, reflectors,

tunable solid-state lasers N. Tamaoki, Adv Mater, 13, 1135 (2001)

N. Tamaoki et al, J. Mater. Chem., 2001, 11, 1003

N. Tamaoki et al, J. Phys. Chem. B 107, 12054 (2003)

P; helical pitch

Β; HTP

C; solute conc.

2

Liquid crystals

Novel functional liquid crystalline materials - Liquid crystalline semiconducting materials for organic electronics (OFETs)

- Photoresponsive dopants and cholesteric LCs photoisomerizable / chiral dopant ; colorful pitch, mechanical work induction applications

Kim, Wada, Tamaoki, J. Mater. Chem. C, 2014, 2, 1921.

Kim and Tamaoki, J. Mater. Chem. C., 2014, 2, 9258.

Kim, Funahashi, Tamaoki, RSC Adv., 2014, 4, 60511

Cholesteric host

Achiral dopant

Previous study…

300 400 500 600 700 8000

20

40

60

80

100

W/O UV irradiation

Tra

nsm

itta

nce /

%

Wavelength / nm

Time / hour0

1

2

3

4

16

20

25

45

60

90

75 80 85 90 95 100 105 110 115 120400

500

600

700

800

900

1000

m

ax / n

m

Temperature / oC

4

trans- and cis- isomerization

Previous study…

Achieving large helical twisting power

Photo-switching

AZO Cholesterol

chirality photoisomerization

*Smaller size of smectic cluster; shorter pitch and higher HTP

Cooperative effect

of the conformation and molecular chirality

- cis isomers associated with larger HTPs

Initial state PSS365nm PSS436nm

Simple synthetic route with inexpensive starting materials

Nematic LC host (NLC); JC-1014XX, E7, and 5CB LED UV power; 0.3 W -> 0.31mW/mm2

Dopant; naphthopyran derivative obtained from Dr. Michel Frigoli

Photo-induced HTP and rotational motion switching from naphthopyran derivative

First-order exponential relaxation of the pitch with time (wedge cell, 0.2%)

0 2 4 6 8 10 12 140

20

40

60

80

100

120

Pitch

, m

km

Day

y = y0 + A1*exp(-x/t1)

y0 = 12.3

A1 = 95.8008

t1 = 5.57951

UV

300 400 500 600 7000.0

0.2

0.4

0.6

abso

rban

ce

initial

after 19 h

after 65 h

after 89 h

after 113 h

after 137 h

after 161 h

after 233 h

after 281 h

after 329 h

after 401 h

after 449 h

/ nm

a

0 100 200 300 400

0.00

0.04

0.08

0.12

0.16

abso

rban

ce

t / h

E7

Thermal back in toluene

Data from Dr. Michel Frigoli 0 20 40 60 80 100 120

0

20

40

60

80

100

120

Pitch

, m

km

Irradiation time, min

UVWhite light

wedge cell 0.5%

NLC HTP (β), μm-1

Initial PSS365nm |Δβ|/βini

JC-1014XX 28.5 2.0 93.0 %

E7 26.4 1.8 93.2 %

5CB 20.0 1.5 92.5 %

HTPs of naphthopyran before and after UV irradiation in NLC hosts

Ref; 25 min irr. 1mW/mm2 HTP in E7; 40.8-> 4.7 μm-1 |Δβ|/βini value of 88.5 % by UV

a b c d

Continuous UV light irradiation onto the CLC mixture film (0.21 wt% in E7) from a to h for 17.5 min resulted in the rotational motion of a micro glass rod for 3.5 cycles (1260 o).

e f g h

Experimental details referred to Y. Kim and N. Tamaoki, J. Mater. Chem. C, 2014, 2, 9258–9264

Upon UV irradiation,

After 72 hr

Monitoring thermal back reaction for a week

UV off

24 hr

24 hr 24 hr

UV PSS

a b c d e

f g h i j

k l m n o

Continuous UV light irradiation onto the CLC mixture film (0.6 wt% in E7) from a to g for 5 min resulted in the anti-clockwise rotational motion of a micro glass rod for 3 cycles (1080 o). Subsequently, UV light source was turned off from h to o resulting in thermal back clockwise rotational motion exhibiting 300 o rotation for 24 hours .

0 5 10 15 20 25750

800

850

900

950

1000

1050

1100

Ro

tati

on

an

gle

(d

eg

)

Time (h)

0 1 2 3 4 5

0

200

400

600

800

1000

1200

UV irradiation time (m)

Ro

tati

on

an

gle

(d

eg

)

28 % decrease (recovery)

0 2 4 6 8 10 12 140

20

40

60

80

100

120

Pitch, m

km

Day

y = y0 + A1*exp(-x/t1)

y0 = 12.3

A1 = 95.8008

t1 = 5.57951

UV

36 % decrease

Thermal back from previous report; 30% decrease (keep 60 hrs at darkroom)

~16 % in 24 hrs

10 min

12 hr 4 hr 6 hr

12 o

125 o 189 o 206 o

18 % decrease in 22 hrs 0 5 10 15 20 25

950

1000

1050

1100

1150

Ro

tati

on

al

an

gle

, d

eg

Time, h

Equation

y = Intercept + B1*x^1 + B2*x^2

Weight No Weighting

Residual Sum of Squares

558.91354

Adj. R-Square 0.97005

Value Standard Error

?$OP:A=1 Intercept 1145.92248 11.92788

?$OP:A=1 B1 -13.19671 3.1016

?$OP:A=1 B2 0.17433 0.14832

Upon UV; 1150 o initial

T. back

CLC mixture film (0.6 wt% in E7)

Ionic dimeric CLCs which can undergo photo- or/and electrochemically- driven macroscale reorganization

Azobenzene bridged with redox active-viologen compound

Ionic CLCs which can undergo photo- or/and electrochemically- driven macroscale reorganization

Chiral units inducing cholesteric LC

containing redox-active units without redox-driven interconversion properties redox- active units undergoing interconversion: dynamic redox process

chiral

DCC, DMAP DCM, 24h at RT

THF, 24h at 40 oC

Synthetic scheme

From previous report,

KI, K2CO3

acetone Reflux 24 hr

DCM, reflux 48 hr

Yield; 80 %

PdCl2(dppf), Na2CO3, DMF/H2O, 95 °C

1,2-benzenedithiol, TsOH, benzene, reflux

Zn, CH2Cl2/THF, rt.

4 equiv of (p-BrC6H4)3N+•SbCl6

−, MeCN/CH2Cl2, rt

R=chiral mesogen group

i) n-BuLi, ii) CuCl, reflux

Bromine, RT

i) n-BuLi, ii) H2O

Redox-driven switch dopant precursor synthesis

i) n-BuLi, ii) DMF iii) HCl aq sln

Yield; 53 % 1H NMR matched to the ref. (Synth. Lett. 2007, 15, 2390-2394)

Yield; 40 % 1H NMR matched to the ref. (Synth. Lett. 2007, 15, 2390-2394)

Future work

Naphthopyran chiral dopant; Confirmation and analysis of thermal back behavior from rotational motion experiment

Synthesis