Multichannel Sensors Based on Biphenyl and Cyclohexane Conformational Changes - Designing Receptors for the Next Generation of Biosensors - page 4

N N

N

-1e - -1e -

N N

N

TMB Radical cation TMBOx

Scheme 1 Oxidation of N , N , N 0 , N 0 -tetramethylbenzidine (TMB)

N

N

77.9 deg.

34.2

N

N

N

N

Fig. 2 Dihedral angle in TMB and 2,2 0 -disustituted TMB

N

N

N

N

N

N

Fig. 3 Influence of the dihedral angle in the fluorescence emission of TMB derivatives

addition of Ni 2+ ,Cu 2+ ,Zn 2+ ,Cd 2+ , and Hg 2+ metal ions induces a partial quenching
of the emission band centered at 370 nm. Conversely in the presence of Pb 2+ , both
ligands undergo a selective red shift of the emission band of ca. 50 nm (Fig. 4 ).
Compound 3 also displays selective behavior. Thus, the presence of Cu 2+ produces