Controlled Charge Transport and Charge Storage in Polyarylamine Redox Arrays

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1 Controlled Charge Transport and Charge Storage in Polyarylamine Redox Arrays Department of Chemistry, The University of Alabama Kye-Young Kim, Trent D. Selby, Greg Szulczewski*, Silas C. Blackstock* funding: SF-MRSEC seed project

2 Charge Transport and Storage in a Redox Gradient Array oxidant e - shell oxidation internal CT higher E o lower E o hν(ct) + reductant e -

3 PTe Shell/Core Dendrimers PTe 6PD / 1PTe 6AA/PTe [MW 927] E o '(1) = 0.32 V E o '(2) = 0.67 V E o '(3) = 1.07 V E o '(4) = 1.29 V = [MW 3384] E o (1) = 0.36 V E o (2,3,4) = 0.53 V E o (5,6,7) = 0.63 V E o (8) = 0.88 V = [MW 2201] E o '(1) o '(1) = V E o '(2) o '(2) = V E o '(3,4,5) = 0.86 V

4 3-Tier Tier Redox Redox Gradient Gradient Dendrimer Dendrimer = [MW 5931] E o '(1) = 0.36V E o '(2, 3,4) = 0.55 V E o '(5,6,7) = 0.62 V E o '(8-13) = 0.88 V 0.1 M TBABF 4 in CH 2 Cl 2, E vs SCE E o shell =.67 V E o middle =.48 V E o core =.36 V 12AA/6PD/PTe

5 Synthesis of Redox Arrays H excess Cu, K 2 CO 3, H H H 0.4 eq. Cu, K 2 CO 3, H = 61% 30% 0.3 eq. 0.3 eq. Cu, K 2 CO 3, Cu, K 2 CO 3, PTe 56% 6PD/PTe 60%

6 Synthesis of Bigger Core/Shell Arrays H 2 H 2 Cl 4 Cu, K 2 CO 3, 52% Cl H 2 Pd 2 (dba) 3, t-bu 3 P,aO-t-Bu 80% H excess Cu, K 2 CO 3, Ph 2 O, 52% = = 1/3 eq. H H H Pd 2 (dba) 3, t-bu 3 P ao-t-bu 41% 6AA/PTe 48% Cu, K 2 CO 3, 0.4 eq. 12AA/6PD/PTe 24% 1/3 eq. Cu, K 2 CO 3, H

Charge njection of PTe Core film on TO glass (µa) -8-6 -4-2 0 2 4 CV in solution 0 200 400 600 800 1000 1200 1400 E (mv) vs. SCE E o '(1) = 0.22 V E o '(2) = 0.56 V E o '(3) = 0.96 V E o '(4) = 1.

7 Charge njection of PTe Core film on TO glass (µa) CV in solution E (mv) vs. SCE E o '(1) = 0.22 V E o '(2) = 0.56 V E o '(3) = 0.96 V E o '(4) = 1.18 V n aclo 4 /CH 2 Cl 2 Q (mc) Charging of 300 nm film ( mol) on TO glass by CPC in aclo 4 /H 2 O time (min) E = 0.63 V E = 0.45 V PT e - /molecule PT e - /molecule

8 Charge Migration in a core film - Charge migrates and equilibrates immediately. PTe room temp. 50 C, 10 min ; PTe 0 +1 : PTe + by CPC at 0.45 V +2 : PTe 2+ by CPC at 0.63 V 0.1 M aclo 4 /H 2 O 70 C, 10 min

9 Charge Migration in a Shell/Core film - Charge migrates slowly in an electrolyte solution. 6PD/PTe room temp. 50 C, 30 min : 6PD/ PTe 0 +1 : 6PD/PTe +, CPC at 0.50 V +7 : 6PD +6 /PTe +, CPC at 0.65 V mol on TO glass 0.1 M aclo 4 /H 2 O 70 C, 30 min

Charge Migration in a 3-tier 3 array film

50 C, 30 min 0 0 +1 +1 +7 +7 +1 : CPC at 0.

10 Charge Migration in a 3-tier 3 array film 12AA/6PD/PTe - charge transport between the cores of molecules is very poor due to shells. room temp. 50 C, 30 min : CPC at 0.55 V +7 : CPC at 0.65 V mol on TO glass 0.1 M aclo 4 /H 2 O 70 C, 30 min

11 Summary Several redox-gradient shell/core arrays have been synthesized and their electronic properties were studied. Cationic charge can be trapped exclusively at the core of the shell/core arrays. Charge migration between molecules in shell/core films is poor due to high shell/core exchange barrier. Charge transport and storage can be directed by proper shell/core design.

12 Thiol Attached Polyarylamine Redox-Gradient Dendrimer - goal : covalently attach the monolayer to a conducting surface - approach : attach thiol linker to the redox-gradient array

13 SH Attached Target RG SH Attached Target RG-Arrays Arrays SH S-4AA/PD SH S-TAPD HS SH 2S-4AA/PD SH 4AA/S-PD

14 Synthesis of SH-attached TAPD excess H Cu, K 2 CO 3, 61% H 2 Pd(dba) 2 P(tBu) 3 aotbu 66% H O S Cl O 1) Zn, Me 2 SiCl 2, DMA (ClCH 2 ) 2, 75 o C 2) K 2 CO 3, PhCH 2 Cl, 75 o C 76% S Pd(dba) 2 P(tBu) 3 aotbu 82% S H Bn S S-TAPD 59% a, H o C

15 Electrochemistry of S-TAPDS CV of S-TAPD in solution -8-6 SH E o '(1) = 0.45 V E o '(2) = 0.83 V TBABF 4 /CH 3 C Pt electrode (µa) E vs SCE (mv) CV of S-TAPD Monolayer on Au TAPD S S S S Au/SiO 2 /Si E o '(1) = 0.58 V E o '(2) = 0.91 V TBABF 4 /CH 3 C (µa) E vs SCE (mv)

16 Future Work - Preparation and characterization of SH attached shell/core array is underway. - S-attached redox-gradient monolayer will be studied by STM.

17 Publications 1. Patterned Redox Arrays of Poly Arylamines. The Synthesis and Electrochemistry of p-phenylenediamine (PD) and Arylamino (AA) Appended PD Arrays Trent D. Selby, Kye-Young Kim, and Silas C. Blackstock in press. Chem. Mater April issue 2. Patterned Redox Arrays of Poly Arylamines. Growth of Thin Films and their Electrochemical Behavior. Kye-Young Kim, Joel D. Hassenzahl, Trent D. Selby, Greg J. Szulczewski and Silas C. Blackstock in press. Chem. Mater April issue 3. A Three-Tier Redox-Gradient Dendrimer. Redox Arrays Designed for Directional Charge Transport and Storage Trent D. Selby, Kye-Young Kim, and Silas C. Blackstock in preparation for J. Am. Chem. Soc.

Redox- Gradient Dendrimer

Charge Storage in a 3-tier3 Redox- Gradient Dendrimer The Center for Materials for Information Technology and the Department of Chemistry, Kye-Young Kim and Silas C. Blackstock* Fall Review, ovember 2002