title: Determination of the ground state, excited state and change in dipole moments of magnesium and zinc chlorin.
abstract: High-resolution Stark effect measurements on the S1 <-- S0 (pi pi*) origin of magnesium chlorin (MgCh) and zinc chlorin (ZnCh) in single crystals of n-octane at 4.2 K are reported. The corresponding change in dipole moment (absolute value(delta mu(ge))) associated with each transition was estimated to be 0.23 +/- 0.04 and 0.27 +/- 0.05 debye, respectively. Each molecule's orientation in the n-octane crystal was also determined. The change in dipole moment of MgCh was also found using solvatochromic shift data (absolute value(delta mu(ge))) = 0.33 +/- 0.08 debye). The ground state dipole moment (mu(g)) of MgCh was determined by dielectric constant measurement of MgCh/benzene solutions (mu(g) = 2.26 +/- 0.08 debye). These were combined to calculate the average excited state dipole moment of MgCh (mu(e) = 2.51 +/- 0.08 debye). The ground state dipole moment of ZnCh was also determined using solvatochromic shift data (mu(g) = 3.17 +/- 0.08 debye). This was combined with its measured absolute value(delta mu(ge)) to calculate the excited state dipole moment of ZnCh (mu(e) = 3.44 +/- 0.08 debye); the S1 <-- S0 (pi pi*) origin band of both complexes was red-shifted at room temperature as the polarity of the solvents was increased, which implies that delta mu(ge) is positive.
authors.forename: Amarnauth
authors.initials: A
authors.lastname: Singh
authors.forename: Wen-Ying
authors.initials: WY
authors.lastname: Huang
authors.forename: Lawrence W
authors.initials: LW
authors.lastname: Johnson
mesh_terms: D004563:Electrochemistry / Q000379:methods; D007700:Kinetics; D008274:Magnesium; D008958:Models, Molecular; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D012996:Solutions; D012997:Solvents; D015032:Zinc
chemical_list: D011166:Porphyrins; D012996:Solutions; D012997:Solvents; C006969:chlorin; D008274:Magnesium; D015032:Zinc