On the ultrafast charge migration and subsequent charge directed reactivity in Cl center dot center dot center dot N halogen-bonded clusters following vertical ionization

In this article, we have presented ultrafast charge transfer dynamics through halogen bonds following vertical ionization of representative halogen bonded clusters. Subsequent hole directed reactivity of the radical cations of halogen bonded clusters is also discussed. Furthermore, we have examined effect of the halogen bond strength on the electron-electron correlation-and relaxation-driven charge migration in halogen bonded complexes. For this study, we have selected A-Cl (A represents F, OH, CN, NH2, CF3, and COOH substituents) molecules paired with NH3 (referred as ACl:NH3 complex): these complexes exhibit halogen bonds. To the best of our knowledge, this is the first report on purely electron correlation-and relaxation-driven ultrafast (attosecond) charge migration dynamics through halogen bonds. Both density functional theory and complete active space self-consistent field theory with 6-31+G(d, p) basis set are employed for this work. Upon vertical ionization of NCCl center dot center dot center dot NH3 complex, the hole is predicted to migrate from the NH3-end to the ClCN-end of the NCCl center dot center dot center dot NH3 complex in approximately 0.5 fs on the D-0 cationic surface. This hole migration leads to structural rearrangement of the halogen bonded complex, yielding hydrogen bonding interaction stronger than the halogen bonding interaction on the same cationic surface. Other halogen bonded complexes, such as H2NCl:NH3, F3CCl:NH3, and HOOCCl:NH3, exhibit similar charge migration following vertical ionization. On the contrary, FCl:NH3 and HOCl:NH3 complexes do not exhibit any charge migration following vertical ionization to the D-0 cation state, pointing to interesting halogen bond strength-dependent charge migration. (C) 2015 AIP Publishing LLC.

Tracking the migration of the Indian continent using the carbonate clumped isotope technique on Phanerozoic soil carbonates

Approximately 140 million years ago, the Indian plate separated from Gondwana and migrated by almost 90 degrees latitude to its current location, forming the Himalayan-Tibetan system. Large discrepancies exist in the rate of migration of Indian plate during Phanerozoic. Here we describe a new approach to paleo-latitudinal reconstruction based on simultaneous determination of carbonate formation temperature and delta O-18 of soil carbonates, constrained by the abundances of C-13-O-18 bonds in palaeosol carbonates. Assuming that the palaeosol carbonates have a strong relationship with the composition of the meteoric water, delta O-18 carbonate of palaeosol can constrain paleo-latitudinal position. Weighted mean annual rainfall delta O-18 water values measured at several stations across the southern latitudes are used to derive a polynomial equation: delta(18)Ow = -0.006 x (LAT)(2) - 0.294 x (LAT) - 5.29 which is used for latitudinal reconstruction. We use this approach to show the northward migration of the Indian plate from 46.8 +/- 5.8 degrees S during the Permian (269 M. y.) to 30 +/- 11 degrees S during the Triassic (248 M. y.), 14.7 +/- 8.7 degrees S during the early Cretaceous (135 M. y.), and 28 +/- 8.8 degrees S during the late Cretaceous ( 68 M. y.). Soil carbonate delta O-18 provides an alternative method for tracing the latitudinal position of Indian plate in the past and the estimates are consistent with the paleo-magnetic records which document the position of Indian plate prior to 135 +/- 3 M. y.