A series of tripler di(2,6-dimethylphenyl)carbenes ((3)2) bearing nine symmetrical para di-substituents with well-distributed electronic properties have been generated by the irradiation of the corresponding diazo precursors and studied using electron paramagnetic resonance spectroscopy. The zero field splitting parameters, D and E, were measured in matrices of different viscosities and are analyzed in terms of a sigma-dot (sigma(.)) scale of spin-delocalization substituent constants. Fairly good correlation (r > 0.9) with sigma(.) based on the spin delocalization in the absence of polar effects was found for the D values of (3)2 in its minimum energy geometry, but not for those in the metastable state. The magnitude of rho for (3)2 was larger than that for o-unsubstituted diphenylcarbenes and is discussed in terms of the difference in the geometry between the two carbene systems.