Semiempirical ZINDO

Semiempirical ZINDO/CV calculations have suggested that the quadratic hyperpolarizability of dimers and trimers are about one order of magnitude higher than that of the monomer [182], A DFT/TDDFT investigation on the NLO chromo-phores 57b and 58b [183] has confirmed an almost planar architecture, which enhances the 7i-conjugation of the push-pull system and, as a cmisequence, the quadratic hyperpolarizability. 

The well-established semiempirical ZINDO/S method has been used to calculate the hole and electron transfer matrix elements for all the selected dimers. Both and show a monotonic decreasing behavior due to the fact that the interaction... 

Caricato, M.,Andreussi, 0., and Corni, S. (2006] Semiempirical (ZINDO-PCM] approach to predict the radiative and nonradiative decay rates of a molecule close to metal particles, / Phys. Chem. B, 110, 16652-16659. 

The most accurate computations of the intermolecular coupling are carried out at the DFT level of theory (usually involving hybrid functionals such as B3LYP) with the molecular orbital expanded in a medium to large atomic basis set. Less accurate but very fast computations are done using the semiempirical ZINDO Hamiltonian which has been optimized for electronic spectroscopy and has been validated against DFT a number of times [92]. More elementary extended Htickel computations were... 

The semiempirical techniques available include EH, CNDO, INDO, MINDO/3, ZINDO, MNDO, AMI, and PM3. The ZINDO/S, MNDO/d, and PM3(TM) variations are also available. The semiempirical module seems to be rather robust in that it did well on some technically difficult test calculations. 

Semiempirical (CNDO, MNDO, ZINDO, AMI, PM3, PM3(tm) and others) methods based on the Hartree-Fock self-consistent field (HF-SCF) model, which treats valence electrons only and contains approximations to simplify (and shorten the time of) calculations. Semiempirical methods are parameterized to fit experimental results, and the PM3(tm) method treats transition metals. Treats systems of up to 200 atoms. 

Semiempirical methods are widely used, based on zero differential overlap (ZDO) approximations which assume that the products of two different basis functions for the same electron, related to different atoms, are equal to zero [21]. The use of semiempirical methods, like MNDO, ZINDO, etc., reduces the calculations to about integrals. This approach, however, causes certain errors that should be compensated by assigning empirical parameters to the integrals. The limited sets of parameters available, in particular for transition metals, make the semiempirical methods of limited use. Moreover, for TM systems the self-consistent field (SCF) procedures are hardly convergent because atoms with partly filled d shells have many... 

More advanced semiempirical molecular orbital methods have also been used in this respect in modeling, e.g., the structure of a diphosphonium extractant in the gas phase, and then the percentage extraction of zinc ion-pair complexes was correlated with the calculated energy of association of the ion pairs [29]. Semiempirical SCF calculations, used to study structure, conformational changes and hydration of hydroxyoximes as extractants of copper, appeared helpful in interpreting their interfacial activity and the rate of extraction [30]. Similar (PM3, ZINDO) methods were also used to model the structure of some commercial extractants (pyridine dicarboxylates, pyridyloctanoates, jS-diketones, hydroxyoximes), as well as the effects of their hydration and association with modifiers (alcohols, )S-diketones) on their thermodynamic and interfacial activity [31 33]. In addition, the structure of copper complexes with these extractants was calculated [32]. 

That said above does not mean that a semiempirical parameterization based on the HFR MO LCAO scheme and valid for a certain narrow class of compounds or even for a specific purpose cannot be built. It is done for example in [69] for iron(H) porphyrins. But in a more general case there is no way to arrive to any definite conclusion [76] about the validity of a semiempirical parameterization in the HFR context. On the other hand we have to mention that the semiempirical method ZINDO/1 [77] which allows for... 

M. C. Zerner and co-workers, ZINDO A Semiempirical Program Package, University of Florida, Gainesville, FL 32611, USA. 

Table 6.5 Calculated and experimental [114] UV spectra of methylenecyclopropene. The semiempirical calculations were done with ZINDO/S in G94W the ab initio results are from Table 5.16...

INDO/S Kotzian M, RoschN, Zemer MC (1992) Theor Chim Acta 81 201 (b) ZINDO/S is a version of INDO/S with some modifications, plus the ability to handle transition metals. The Z comes from the name of the late Professor Michael C. Zemer, whose group developed the suite of (mostly semiempirical) programs called ZINDO, which includes ZINDO/S. ZINDO is available from, e.g., Molecular Simulations Inc., San Diego, CA, and CAChe Scientific, Beaverton, OR. INDO and ZINDO are available in some program suites, e.g. Gaussian [55]... 

The highly specific behavior of transition metal complexes has prompted numerous attempts to access this Holy Grail of the semi-empirical theory - the description of TMCs. From the point of view of the standard HFR-based semiempirical theory, the main obstacle is the number of integrals involving the d- AOs of the metal atoms to be taken into consideration. The attempts to cope with these problems have been documented from the early days of the development of semiempirical quantum chemistry. In the 1970s, Clack and coworkers [78-80] proposed to extend the CNDO and INDO parametrizations by Pople and Beveridge [39] to transition elements. Now this is an extensive sector of semiempirical methods, differing by expedients of parametrizations of the HFR approximation in the valence basis. These are, for example, in methods of ZINDO/1, SAMI, MNDO(d), PM3(tm), PM3 etc. [74,81-86], From the... 

Probably, Mike s research has most touched other scientists through his development of ZINDO, the semiempirical molecular orbital method and... 

ZINDO57-58 is a semiempirical intermediate neglect of differential overlap/spectroscopy (INDO/S) based routine. It can be combined with an SOS method to calculate second-order nonlinear optical coefficients. ZINDO is parametrized to accommodate transition-metal calculations and is therefore suited for calculation on organometallic compounds. To achieve computational efficiency, some of the terms in Eq. (2) are replaced by empirical data or neglected. To see how the INDO/S does this, the closed-shell case will be examined.57 58 It is useful to introduce the following ... 

In general, CNDO/2, INDO, and PRDDO mimic ab initio results by artful and compensating approximations and semiempirical parameters, and they yield reasonable dipole moments and charge distributions. INDO and ZINDO parameterizations are available for relatively many elements in the periodic table, but their predictions can deviate considerably from experiment. 

Graphical pre- and postprocessor for semiempirical molecular orbital programs extended Hiickel, MOPAC, and ZINDO. Structure building from library of fragments and molecules manipulation. Stick, ball-and-stick, and space-filling display. Orbital, electron density, and electrostatic maps. Reaction energy surfaces. IR and UV spectra. MM2 energy minimization. Dynamics. 

Model building, manipulation. Stick, ball-and-stick, space-filling, and dot surface display. Semiempirical calculations by extended Hiickel, CNDO, INDO/1, INDO/S, MINDO/3, MNDO, AMI PM3, ZINDO/1, and ZINDO/S. UV, IR, electrostatic potential, and molecular orbital plots. 2D-to-3D conversion. Protein and DNA fragment libraries. MM4-, BIO-I- (implementations of MM2 and CHARMM, respectively), OPTS, and AMBER molecular mechanics and dynamics. Solvent box. ChemPlus for 3D rendering, conformational searching, modeling biomolecules, computing log P and other QSAR properties. PCs under DOS and Windows. 

Local density functional (LDF) quantum mechanical calculations for materials science. deMon for density functional calculations. Turbomole for Hartree-Fock and MP2 ab initio calculations. ZINDO for extended Fliickel, PPP, CNDO, and INDO semiempirical molecular orbital calculations and prediction of electronic spectra. Plane Wave for band structures of semiconductors. ESOCS for electronic structure of solids. Silicon Graphics and IBM workstation versions. 

Reasonable correlation between measured and calculated TPA was observed for a series of chromophores with medium size [123, 131, 132, 224, 227, 233, 284, 285, 289, 295-300]. However, problems can arise for larger molecules requiring larger Cl space. Under these circumstances, the calculated quantities A/(0. M(y, M02, oi, and 02 may not reliably describe TPA according to Eq. (18). Despite these problems, semiempirical calculations of Im[ (— o. co)] have been the most applied method for a theoretical design of chromophores with large TP absorptivity [131, 132, 233, 283-285, 287-289, 301]. Hence, ZINDO/S-MRDCI has become an attractive theoretical tool for the calculation of TPA due to the modest calculation time. 

---