1.80-1.81Å) and RuCp* complexes of β-substituted porphyrin and porphycene (ca. 1.78-1.79 Å). The molecular structure of 13 exhibits a significant deviation from planarity (Figure ). This is due to the selenophene ring being tilted at an angle of 38.0° to the macrocyclic plane, defined by four meso-carbons. This distortion allows the pyramidal sideon coordination of the palladium(II) ion. The electronic spectrum of ruthenocenoselenaporphyrin 11 (blue in Figure ) displays four bands at 299, 385, 449, and 692 nm. The Soret band at 449 nm is batochromically shifted compared to 21-carbaselenaporphyrin 9 (423 nm, red in Figure ). The electronic absorption spectrum of 14 shows eight bands from 350 to 790 nm, while the palladium(II) of ruthenocenoselenaporphyrin 15 (mixture of two isomers) demonstrates an entirely different spectrum with three bands at 302, 404, and 497 nm (Figure ). The 1 H NMR spectrum of the ruthenium(II) π-complex of 21carba-23-selenaporphyrin 11 indicates its Cs symmetry (Figure ). The resonances of the external macrocyclic ring protons are relocated upfield compared to those of parent macrocycle 9 (Figure ). The external meso-H and selenophene H (12,13) are detected at 7.96 and 7.61 ppm, respectively. The β protons of the pyrrole rings H(7,18) and H (8,17) produce two doublets observed at 7.78 and 6.97 ppm, correspondingly. The outer protons H(2,3) of cyclopentadiene give a doublet at 5.35 ppm, resulting from the scalar coupling with the inner H (21). The inner H( ) proton shows a significant relocation to 3.47 ppm, in contrast to 9 (9-I: -6.53 ppm; 9-II: -4.17 ppm), however similar to the chemical shifts observed for ruthenocene (δ = 4.52 ppm). The positions of the signals indicate a weakening of the diatropic ring current due to the η 5 -π bonding of [RuCp*] + fragment to the cyclopentadiene ring of 9. Notably, the Gradual acidification of compound 11 with a fluoroboric acid diethyl ether complex or trifluoroacetic acid solutions resulted in deep orange monocation 11-H + formation in the first stage, followed by red-brown dication 11-H2 2+ (Scheme 3). The protonation of both pyrrole nitrogen atoms resulted in the relocation of the H(2,3) and H( ) 1 H NMR signals to 5.87 and 1.76 ppm in 11-H2 , respectively (Figure ). The signals of meso, selenophene, and pyrrole hydrogens show downfield transfer to 8.66, 8.03, 8.19, and 7.32 ppm, correspondingly, due to aromatic current amplification. Symmetry lowering of 11-H + due to the protonation of one pyrrole nitrogen atom is reflected in the 1 H NMR spectrum (Figure ). The UV/Vis electronic spectra of 11-H + and 11-H2 2+ are shown in Supporting Information (Figure ). A rare example of stereoselective porphyrin metalation was encountered once ruthenocenoporphyrin 11 was engaged as a macrocyclic ligand. Thus, the reaction with PdCl₂ resulted in the selective formation of a single stereoisomer of 15, presumably 15-B, due to the steric hindrance imparted by the [RuCp*] + fragment (Scheme 2). A feasible conversion to the counterpart was not detected in [D]chloroform (300 K) over 48 hours, as followed by 1 H NMR spectroscopy.