An apparently rigid dibenzothiophene-bridged zinc(II)/magnesium(II) bisporphyrin host (I-M) has been explored for an accurate determination of the absolute configuration of a large series of amino alcohols. At lower substrate concentration, a 1:1 sandwich complex is formed which, upon addition of excess of substrate, converts to the 1:2 host-guest complex with complete inversion of the CD exciton couplet. The intensities of the couplet vary widely just by changing the metal ion (Zn vs Mg) and also-vary between 1:1 and 1:2 host guest complexes. Crystallographic characterizations are reported here :for both 1:1 sandwich and 1:2 host guest complexes using the= same pair of host, and guest, for the first time, which enable us to scrutinize the structural and geometrical changes systematically in rationalizing their optical properties. The intensity of the-CD Couplet is largely dependent on how strongly- the substrate binds with the host and also their mode of binding. No CD couplet is observed in the spectral region of porphyrin absorption when substrate binds in either exo-endo or exo-exo fashion in the 1:2 host guest complex. However, intermolecular H bonding between two encapsulated substrates in the 1:2 host-guest complex stabilizes the endo-endo conformer in which two porphyrin macrocycles are forced to be oriented in a clockwise/anticlockwise direction to produce an intense CD couplet. Such an endoendo binding of (S)-2-aminobutan-1-ol (S-AB) has resulted in a highly intense CD couplet with 11,4g, while no chiroptic response was observed upon changing the metal to zinc, since S-AB would then bind in an exo-endo form. With an increase in the bulk of the substrate, the endo-endo form first transforms into an exo-endo form which, upon further increase in the bulk of the substrate, converts into an exo-exo complex.