In contrast to porphyrins and chlorins, the direct metalation of bacteriochlorins is difficult. Nevertheless, Cu2+ and Zn2+ can be introduced into bacteriopheophytin in acetic acid, whereas Cd2+ can be inserted in dimethylformamide. The former reactions depend on the substituents of the isocyclic ring:  they are facilitated if enolization of the β-ketoester system is inhibited. Starting with [Cd]-bacteriochlorophyll-a or its 132-hydroxy derivative, a series of metallo-bacteriochlorins with central divalent ions Pd2+, Co2+, Ni2+, Cu2+, Zn2+, and Mn2+ have been obtained by transmetalation. Like in the parent Mg complex, the four principal optical transitions are well-separated in these complexes, and their responses to changes in the central metal and its coordination state can be followed in detail. The energies of the Q y and B x transitions are almost independent of the central metal, whereas the Q x and B y transition energies change significantly, depending on the central metal as well as the presence of additional axial ligands. If the complexes are grouped by their coordination number, empirical linear correlations exist between these shifts and the ratio / , where is Pauling's electronegativity value and is the ionic radius of the metal. A similar correlation was found for those 1H NMR signals influenced mainly by the ring current and for the redox potentials. This observation was in contrast with the linear relationships with alone, found for metal-substituted porphyrins. The spectral variations influenced by the central metal and its state of ligation are attributed, within the framework of the four-orbital model, to the electrostatic interaction of the electron densities in the four orbitals with the effective charge of the central metal ions, which is most pronounced for the a2u orbital (HOMO-1). Ligation studies have revealed that addition of the first axial ligand decreases the effective charge of the central metal by approximately 50% and addition of the second axial ligand by another 20% with respect to the absence of axial ligands. The singlet−triplet splitting deduced from fluorescence and phosphorescence measurements is similar for [Pd]-, [Cu]-, [Zn]-, and [Mg]-BChl (4550 ± 100 cm-1).

A method is described for reversibly removing bacteriochlorophyll from the B800-site of the B850-850 antenna complex from Rhodobacter sphaeroides. This method uses the oligosaccharidic detergent Triton BG-10, together with an incubation at pH 5.0. Reconstitution at the B800-site has been successfully achieved for a range of modified bacteriochlorophylls. Copyright 1998 Elsevier Science B.V. All rights reserved.

A method is described which allows the selective release and removal of the Bchla-B800 molecules from the LH2 complex of Rhodopseudomonas acidophila 10050. This procedure also allows reconstitution of approximately 80% of the empty binding sites with native Bchla. As shown by circular dichroism spectroscopy, the overall structures of the B850-only and reconstituted complexes are not affected by the pigment-exchange procedure. The pigments reconstituted into the B800 sites can also efficiently transfer excitation energy to the Bchla-B850 molecules.