Electron tunneling through organic molecules in frozen glasses

Reaction rates extracted from measurements of donor luminescence-quenching by randomly dispersed electron acceptors reveal an exponential decay constant of 1.23 per angstrom for electron tunneling through a frozen toluene glass (with a barrier to tunneling of 1.4 electron volts). The decay is 1.62 per angstrom (the barrier, 2.6 electron volts) in a frozen 2-methyl-tetrahydrofuran glass. Comparison to decay constants for tunneling across covalently linked xylyl (0.76 per angstrom) and alkyl (1.0 per angstrom) bridges leads to conclusion that tunneling between solvent molecules leads to the conclusion that tunneling between solvent molecules separated by similar to2 angstroms (van der WaaLs contact) is 20 to 50 times slower than tunneling through a comparable length of a covalently bonded bridge. Our results provide experimental confirmation that covalently bonded pathway ways can facilitate electron flow through folded polypeptide structures.