Dithiacrown Ether Substituted Porphyrazines: Synthesis, Single-Crystal Structure, and Control of Aggregation in Solution by Complexation of Transition-Metal Ions

The synthesis of novel magnesium, copper, and
metal-free porphyrazines, peripherally substituted with
dithia-7-crown-2 (MPz(7)), dithia-15-crown-5 (MPz(15)), and
dithia-18-crown-6 (MPz(18)) macrocycles is reported.
These compounds are prepared starting from dicyanoethylene
containing crown ethers 3, 2(1), and
2(2), respectively,
which contain sulfur as well as oxygen heteroatoms. The
“crowned” porphyrazines bind silver(I) and
mercury(II) perchlorates. UV/vis spectroscopy and electron paramagnetic
resonance measurements reveal that addition
of the transition-metal ions leads to dimerization of the porphyrazine
complexes. In the case of the dithia-18-crown-6-substituted porphyrazines, the dimers break up to form monomeric
6:1 guest-host complexes when more
than 2 equiv of the metal ion is added. The single-crystal
structures of the crown ether 2(2) and the
porphyrazine
MgPz(18) are presented. Compound
C14H20N2O4S2
(2(2)) crystallizes in the monoclinic space group
P21/c with
a = 10.9310(13) Å, b = 19.383(3)
Å, c = 8.6976(14) Å, β = 108.898(11)°,
V = 1743.5(5) Å3, and Z =
4. The
structure refinement converged to R = 0.0366 and
Rw = 0.0504. Compound
C56H82MgN8O17S8
(MgPz(18))
crystallizes in the triclinic space group P1̄ with
a = 9.584(3) Å, b = 17.672(2) Å,
c = 19.620(4) Å, α = 84.904(14)°, β = 85.21(2)°, γ = 89.29(2)°,
V = 3298.4(13) Å3, and Z =
2. The structure refinement converged to R1
= 0.0839 and wR2 = 0.2196. The electrical properties of
H2Pz(18) have been studied by complex
impedance
spectroscopy. The bulk electrical conductivity of this compound is
approximately 1 order of magnitude higher
than that of the corresponding 18-crown-6 phthalocyanine.