Dear Ezekiel Oyeniyi,

The most accurate calculations to date on ZNS predict a ground state singlet multiplicity.

Peterson KA, Shepler BC, Singleton JM. Mol Phys. 2007;105:1139.

Boughdiri S, Tangour B, Teichteil C, Barthelat JC, Leininger T. Chem Phys Lett. 2008;462:18.

For more information on zinc complexes multiplicity, please see the following text:

Calculated Multiplicities

Generally, all levels of theory correctly predicted the appropriate spin ground states for the Zn species investigated. Open shell species were found to be ground state doublets, and closed shell species ground state singlets. There are two notable exceptions, and these are the cases of ZnO and ZnS. The expected ground state multiplicity, in so far as what species the heat of formation is determined for, is ambiguous. Experimental work indicates that the available heat of formation and Zn-X bond lengths are for the triplet.47,48 However, the most accurate calculations to date on these complexes predict a ground state singlet multiplicity.49,50 The triplet ground state was predicted for ZnO at the CCSD/LACVP**, CCSD(T)/TZVP and CCSD/LANL2DZ-TZVP levels of theory. The triplet was found to be the ground state of ZnS at only the CCSD/LACVP** and CCSD/LANL2DZ-TZVP levels of theory. The pseudopotential incorporating basis sets with the CCSD level of coupled-cluster theory most often arrive at the triplet ground state for both ZnO and ZnS. The lowest errors in calculated ΔHf values were observed using the TZVP and 6–31G** basis sets, which most frequently predict the singlet ground state multiplicities. For ZnO, theoretical studies support a triplet ground state for bond lengths in excess of 1.85A and a singlet for distances closer to the reported internuclear distance of 1.69 Å.50 These findings are in complete agreement with the predicted ground states in our study. Other investigations in our laboratory have turned up similar confusion in predicted ground state spins—in our LANL2DZ investigation,15 a singlet ground state was predicted for all GGA and meta-GGA functionals and triplet ground state for all hybrid-GGA and hybrid-meta-GGA functionals.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903681/

Hoping this will be helpful,

Rafik

Thank you Rafik. This is indeed helpful.