TY - JOUR

T1 - A one-pot synthesis of oligo(arylene-ethynylene)-molecular wires and their use in the further verification of molecular circuit laws

AU - Naher, M.

AU - Gorenskaia, E.

AU - Moggach, S.A.

AU - Becker, T.

AU - Nichols, R.J.

AU - Lambert, C.J.

AU - Low, P.J.

PY - 2022/8/30

Y1 - 2022/8/30

N2 - A convenient two-step, one-pot synthesis of oligo(arylene-ethynylene) (OAE) type molecular wires in yields of up to 70% via in situ desilylation of protected bis(alkynes) Me3SiC≡CArC≡CSiMe3 (Ar = 2,5-thienyl, 1,4-naphthylene, 9,10-anthrylene) and subsequent Sonogashira cross-coupling with S-(4-iodophenyl) ethanethiolate, 4-iodothioanisole, or 5-bromo-3,3-dimethyl-2,3-dihydrobenzo[b]thiophene is described. The in situ desilylation avoids the manipulation of the sensitive terminal dialkynes (HC≡CArC≡CH), whilst the general approach presented has some advantages over alternative synthetic strategies based on coupling of aryl dihalides (XArX) by avoiding the multi-step preparation and purification of the terminal alkynes S-(4-ethynylphenyl) ethanethiolate, 4-ethynylthioanisole and 5-ethynyl 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene. The molecular conductance of the resulting thiolate or thioether functionalised OAE molecular wires has been determined using scanning tunneling microscope break junction (STM-BJ) methods. The trends in molecular conductance do not track simply with the degree of aromaticity of the molecular core despite the rather similar molecular lengths. Rather, the STM-BJ data are better correlated with the nature of the anchor group, highlighting the important role of electrode-molecule coupling on electron transport in a molecular junction. The experimental conductance data are in good agreement with recently described quantum circuit rules, further highlighting the potential for these relationships to be used as predictive tools in molecular electronics research.

AB - A convenient two-step, one-pot synthesis of oligo(arylene-ethynylene) (OAE) type molecular wires in yields of up to 70% via in situ desilylation of protected bis(alkynes) Me3SiC≡CArC≡CSiMe3 (Ar = 2,5-thienyl, 1,4-naphthylene, 9,10-anthrylene) and subsequent Sonogashira cross-coupling with S-(4-iodophenyl) ethanethiolate, 4-iodothioanisole, or 5-bromo-3,3-dimethyl-2,3-dihydrobenzo[b]thiophene is described. The in situ desilylation avoids the manipulation of the sensitive terminal dialkynes (HC≡CArC≡CH), whilst the general approach presented has some advantages over alternative synthetic strategies based on coupling of aryl dihalides (XArX) by avoiding the multi-step preparation and purification of the terminal alkynes S-(4-ethynylphenyl) ethanethiolate, 4-ethynylthioanisole and 5-ethynyl 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene. The molecular conductance of the resulting thiolate or thioether functionalised OAE molecular wires has been determined using scanning tunneling microscope break junction (STM-BJ) methods. The trends in molecular conductance do not track simply with the degree of aromaticity of the molecular core despite the rather similar molecular lengths. Rather, the STM-BJ data are better correlated with the nature of the anchor group, highlighting the important role of electrode-molecule coupling on electron transport in a molecular junction. The experimental conductance data are in good agreement with recently described quantum circuit rules, further highlighting the potential for these relationships to be used as predictive tools in molecular electronics research.

KW - molecular electronics

KW - molecular junction

KW - molecular wire

KW - molecule-electrode coupling

KW - oligo(phenylene-ethynylene)

KW - single-molecule conductance

KW - Sonogashira coupling

KW - STM-break junction

U2 - 10.1071/CH21235

DO - 10.1071/CH21235

M3 - Journal article

VL - 75

SP - 506

EP - 522

JO - Australian Journal of Chemistry

JF - Australian Journal of Chemistry

SN - 0004-9425

IS - 9

ER -