Two state "ON-OFF" NLO switch based on coordination complexes of iron and cobalt containing isomeric ligand: a DFT study.

Coordination complexes are interesting materials for nonlinear optical (NLO) applications due to their large hyperpolarizability values. Moreover, switchable NLO response is also important in coordination complexes. Herein, we report two state ON-OFF switchable NLO contrast of coordination complexes of Fe and Co containing isomeric ligands. The optical, UV-visible, and electronic properties besides the "ON-OFF" switching effect are calculated using the CAM-B3LYP/6-31+G (d) method. The NLO responses of ligand-metal isomers are qualitatively evaluated through variation in charge transference (CT) style through TD-DFT. The higher ß o in each isomeric pair is strongly dependent on the HOMO-LUMO gap. The isomer 4b with lowest HOMO-LUMO gap shows the highest NLO response. The charge transfer pattern in these complexes results in variation of their ß o values. The notable ß o contrast of 21.15 in isomeric pairs 3a and 3b makes these complexes a favorable material for genuine NLO switches. Hence, the outcome of the current investigation reveals that these ligand-metal isomeric complexes exhibit a two-state switch "ON-OFF" effect.

Inclusive DFT insight into sensing mechanism of cyclotetrapyrole towards lung irritants.

The development of smart sensing devices for toxic analytes detection especially lung irritants is much essential. The cyclic conducting polymers having infinite π-conjugation are proved to be highly sensitive for toxic analytes. Herein, by using the DFT approach, we investigated the sensing mechanism of cyclotetrapyrole (CTPy) for accurate detection of phosgene, diphosgene, chloropicrin and chlorine at the B3LYP-D3/6-31 + G (d, p) level. The calculated interaction energies show the physisorption of analytes over the CTPy surface. Natural bond orbital (NBO) and charge decomposition (CDA) analyses predict charge transfer interactions in the complexes. The reduced density gradient (RDG) approach reveals that hydrogen bonding interactions dominate in the complexes. The sensitivity of CTPy towards lung irritants is further illustrated by the reduction in HOMO-LUMO energy gaps, red shifting of [Formula: see text] in UV-Visible spectra. Density of state (DOS) analysis affirm that enhanced conductivity upon complexation is due to the origination of new energy states in occupied and virtual orbitals nearer to the Fermi level. Moreover, PDOS spectra show that CTPy primarily contributes to the energy of HOMO. The outcome of the current study depicts appreciable sensitivity of CTPy towards lung irritants. Moreover, the competing role of naturally occurring atmospheric water is also investigated. We believe that the upshot of the current findings and their forecasts will provide useful guidelines for an experimentalist to design highly sensitive sensors for toxic analytes using CTPy. HIGHLIGHTS: • The highest QNBO transfer towards the analyte (- 0.121) is seen in the chlorine@CTPy complex. • The highest reduction in Eg (61%) between occupied and virtual orbitals is noticed in chlorine@CTPy. • The orbital overlap results in a 41% red shifting of [Formula: see text] in chlorine@CTPy. • Cyclotetrapyrole is highly sensitive for chlorine.

Second-order NLO properties and two-state switching effects of transition metal redox complexes of iron and cobalt: A DFT study.

Designing switchable materials with large contrasts of nonlinear optical properties has been the focus of research in recent decades because of their widespread applications. Redox-active metal complexes due to charge transfer excitation are suitable to produce switchable nonlinear optical (NLO) material. In this regard, we present here the redox switchable NLO response of active metal complexes of iron and cobalt. The geometric, electronic, molecular absorption, nonlinear optical properties, and switch "ON/OFF" style of these metal complexes are studied at the CAM-B3LYP/6-31 + G(d) level of theory. NLO responses of these redox metal complexes are described in terms of change in the charge transfer (CT) patterns by time dependent density functional theory (TD-DFT). The highest ßo value of 301534 × 10-30 esu is noticed in [Fe-ethynyl-ZnP]1+ complex, because of obvious charge transfer transition from metal to ligand i.e meatal-ligand charge transfer (MLCT) in redox metal complex. In each redox metal isomeric pair, the greater hyperpolarizability value of individual isomer is quite consistent with its smaller energy gap (H-Lgap) between highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), low crucial excitation energy, and bathochromic shift of λmax. The remarkable ßo contrasts of these isomeric redox complexes illustrate that they can be appropriate for effective redox-triggered NLO switches. Thus, the results reveal that these redox pair complexes show two-state switching "ON/OFF" effect.

Silver cluster (Ag6) decorated coronene as non-enzymatic sensor for glucose and H2O2.

Silver-graphene quantum dots are promising electrochemical sensors due to their unique electronic properties. Herein, we report the comprehensive DFT study to explore the electronic properties of silver cluster (Ag6) decorated coronene as model for silver graphene quantum dots. The current study aims to investigate the sensing ability of silver-coronene complex for non-enzymatic electrochemical detection of glucose & H2O2. The stability of the complexes of analytes with silver decorated coronene is supported by their greater interaction energies (-36.7 to -44.9 kcal mol-1). NBO charge analysis and charge decomposition analysis (CDA) reveal donor-acceptor charge transfer interactions in the complexes. Frontier molecular orbital analysis illustrates that charge is transferred from analytes to silver decorated coronene during excitation from HOMO to LUMO. The Uv-visible results show that λmax is red shifted during interactions of analytes with silver decorated coronene. The NCI analysis illustrates the strong non-covalent (M … O) and unusual M … H-O interactions in the complexes. The precedent sensing performance of Ag6-coronene might be attributed to the synergistic effect of both silver clusters and coronene in the composite. The evaluated results validate the excellent sensing ability of silver-graphene quantum dots for the detection of glucose & H2O2. The outcome of the current study and its prospects will open the avenue for the rational development of smart sensors.