Hirshfeld density partitioning technique: a first application to the transition metal compounds, HScO, TiO, VO.

We apply a variant of the Hirshfeld density partitioning technique, HI, to calculate the atomic charges and decompose the dipole moments into the part due to the charges and the induced dipoles developed on each atom for three different transition metal (TM) containing molecules. Additionally, the α and ß spin densities are treated separately developing a new variant (spin-adapted HI) of the fractional occupation HI version proposed recently. We also study the dependence of HI charges on the atomic state of the TM employed in the promolecule. The VO case exhibits a strong dependence of the atomic charge on the V or V(+) state used. Although the bonding in the ground high spin electronic state and the first excited low spin state in TiO and VO is essentially identical, the dipole moments differ significantly and we find that this is due entirely to the σ electron distribution localized on the transition metal. Finally, the mechanism for the rapid change of the dipole moment of HScO upon bending is confirmed to occur mainly due to the induced atomic charges.

Ground and excited states of vanadium hydroxide isomers and their cations, VOH(0,+) and HVO(0,+).

Employing correlation consistent basis sets of quadruple-zeta quality and applying both multireference configuration interaction and single-reference coupled cluster methodologies, we studied the electronic and geometrical structure of the [V,O,H](0,+) species. The electronic structure of HVO(0,+) is explained by considering a hydrogen atom approaching VO(0,+), while VOH(0,+) molecules are viewed in terms of the interaction of V(+,2+) with OH(-). The potential energy curves for H-VO(0,+) and V(0,+)-OH have been constructed as functions of the distance between the interacting subunits, and the potential energy curves have also been determined as functions of the H-V-O angle. For the stationary points that we have located, we report energies, geometries, harmonic frequencies, and dipole moments. We find that the most stable bent HVO(0,+) structure is lower in energy than any of the linear HVO(0,+) structures. Similarly, the most stable state of bent VOH is lower in energy than the linear structures, but linear VOH(+) is lower in energy than bent VOH(+). The global minimum on the potential energy surface for the neutral species is the X(3)A" state of bent HVO, although the X(5)A" state of bent VOH is less than 5 kcal/mol higher in energy. The global minimum on the potential surface for the cation is the X(4)Σ(-) state of linear VOH(+), with bent VOH(+) and bent HVO(+) both more than 10 kcal/mol higher in energy. For the neutral species, the bent geometries exhibit significantly higher dipole moments than the linear structures.

Ab initio investigation of titanium hydroxide isomers and their cations, TiOH(0,+) and HTiO(0,+).

We studied the electronic and geometrical structure of the [Ti, O, H](0,+) species, using large basis sets and both single-reference coupled cluster and multireference configuration interaction methodologies. The electronic structure of HTiO(0,+) is interpreted qualitatively in terms of a hydrogen atom bonding to TiO(0,+), while the structure of TiOH(0,+) is interpreted in terms of Ti(+,2+) bonding to OH(-). Potential energy profiles are reported as functions of the Ti-OH and H-TiO bond lengths, and of the H-Ti-O angle. For a total of 33 stationary points on the potential energy surfaces, we report absolute energies, geometries, and harmonic frequencies. For the neutral species, dipole moments are also given.

A Hirshfeld-I interpretation of the charge distribution, dipole and quadrupole moments of the halogenated acetylenes FCCH, ClCCH, BrCCH, and ICCH.

We report the dipole and quadrupole moments of the halogenated acetylenes calculated using large basis sets and the SCF, DFT(B3LYP), and CCSD methods, and we analyze the charge density using the Hirshfeld and Hirshfeld-I techniques. The atomic charges, dipoles, and quadrupoles resulting from the Hirshfeld-I analysis are used to interpret the unusually small molecular dipole moments in the sequence as well as the molecular quadrupole moments. The very small dipoles obtain for two reasons. First, the dipole moment associated with the σ and π electron densities is comparable in magnitude and opposite in direction. Second, the charge and induced dipole contributions for ClCCH, BrCCH, and ICCH have opposite signs further reducing the molecular dipoles. The molecular quadrupole moments are the sum of a charge, atomic dipole, and in situ quadrupole terms, and are dominated by the atomic dipoles and in situ quadrupoles with the charge contributions playing an unexpectedly minor role.

A Hirshfeld interpretation of the charge, spin distribution, and polarity of the dipole moment of the open shell (3Sigma-) nitrogen halides: NF, NCl, and NBr.

We calculated the dipole moment function for the ground (3)Sigma(-)(m(S) = +1) state of the open shell molecules, NF, NCl, and NBr, and analyzed it in terms of the charge and spin distribution and the induced atomic dipoles using the Hirshfeld partitioning of the electron density. The smallest dipole moment (0.026ea(0)) obtains with NF, in which the atoms have the largest difference in electronegativity, while the dipole moments in NCl and NBr are 0.441ea(0) and 0.506ea(0), respectively. All dipoles have the N(-)X(+) polarity. In the sigma system alpha spin electrons flow from N to the halogen while beta spin electrons flow in the opposite direction and interestingly from both the sigma and the pi systems of the halogen to the sigma system of N. In NF the number of beta spins lost by F is essentially equal to the number of alpha spins gained and the atomic charges are essentially 0. The small dipole in NF is the result of a slight imbalance in the induced atomic dipoles. For NCl and NBr the halogen loses more beta spins than it gains alpha spins resulting in the polarity N(-)X(+). It is interesting that at equilibrium N gained electrons in the pi system while the halogen lost pi electrons relative to the separated atoms. This however is not back donation in the usual sense because the electrons gained by N have alpha spin while those lost by the halogen have beta spin. Detailed examination of the spin flow shows that the excess alpha electrons in the pi system of N come from an intra-atomic transfer from the N sigma system. The induced atomic dipole moments essentially cancel at all internuclear separations and the polarity of the dipole moment accurately reflects the molecular charge distribution.

Hypertension and hyperlipidemia management in patients treated at community health centers.

OBJECTIVE: Community health centers (HCs) provide care for millions of medically underserved Americans with disproportionate burdens of hypertension and hyperlipidemia. For both conditions, treatment guidelines recently became more stringent and quality improvement (QI) efforts have intensified. We assessed hypertension and hyperlipidemia management in HCs during this time of guideline revision and increased QI efforts. DESIGN: Cross-sectional chart review. SETTING AND PARTICIPANTS: Eleven Midwestern HCs for 2000 and 9 for 2002 provided audit data from 2,976 randomly chosen patients with hypertension and/or hyperlipidemia. MEASUREMENT: Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC VI/VII) and National Cholesterol Education Program Adult Treatment Panel (NCEP-ATP III) guidelines were used to assess management of these conditions. RESULTS: Hypertension (2000, N=808; 2002, N=692) and hyperlipidemia (2000, N=774; 2002, N=702) outcomes improved for specific clinical subgroups. Hypertensive patients with 1 or more cardiovascular risk factors demonstrated significant improvement (34% vs. 45% controlled at <140/90 mm Hg, p=0.02). Hypertension control for persons with diabetes, renal failure and heart failure increased (16% vs. 28% controlled at <130/85 mm Hg, p=0.006). LDL control increased significantly for patients with 2 or more risk factors (39% vs. 58% controlled at <130 mg/dl, p=0.008). Other clinical subgroups showed trends toward better control, although there was insufficient power to detect significant differences for these groups. CONCLUSION: Hypertension and hyperlipidemia outcomes improved for some risk groups; however, ongoing QI is necessary.

Providers' assessment of barriers to effective management of hypertension and hyperlipidemia in community health centers.

We explored 251 providers' (47% licensed practical nurses, 27% registered nurses, 10% physicians, 10% physician assistants, 6% other) perceptions of barriers to effective management of hypertension and hyperlipidemia from 72 Midwest community health centers (CHCs). Optimal care for these diseases is difficult in any setting; little is known about the specific barriers CHCs face. Community health centers often have a multidisciplinary team that participates in patient care. Current models of quality improvement and chronic care management require virtually all CHC providers to know clinical guidelines. Providers in this study generally chose hypertension and hyperlipidemia target levels that met or were more stringent than national guidelines, but lacked confidence to address behavioral change and reported obstacles to modifying patient lifestyle. Community health centers should strengthen providers' skills in facilitating lifestyle change. Improving quality of care requires supporting providers' efforts to take patients' psychosocial and financial challenges into account, and revised policies to eliminate financial and cultural barriers to care.

Improving diabetes care in midwest community health centers with the health disparities collaborative.

OBJECTIVE: To evaluate the Diabetes Health Disparities Collaborative, an initiative by the Bureau of Primary Health Care to reduce health disparities and improve the quality of diabetes care in community health centers. RESEARCH DESIGN AND METHODS: One year before- after trial. Beginning in 1998, 19 Midwestern health centers undertook a diabetes quality improvement initiative based on a model including rapid Plan-Do-Study-Act cycles from the continuous quality improvement field; a Chronic Care Model emphasizing patient self-management, delivery system redesign, decision support, clinical information systems, leadership, health system organization, and community outreach; and collaborative learning sessions. We reviewed charts of 969 random adults for American Diabetes Association standards, surveyed 79 diabetes quality improvement team members, and performed qualitative interviews. RESULTS: The performance of several key processes of care assessed by chart review increased, including rates of HbA(1c) measurement (80-90%; adjusted odds ratio 2.1, 95% CI 1.6-2.8), eye examination referral (36-47%; 1.6, 1.1-2.3), foot examination (40-64%; 2.7, 1.8-4.1), and lipid assessment (55-66%; 1.6, 1.1-2.3). Mean value of HbA(1c) tended to improve (8.5-8.3%; difference -0.2, 95% CI -0.4 to 0.03). Over 90% of survey respondents stated that the Diabetes Collaborative was worth the effort and was successful. Major challenges included needing more time and resources, initial difficulty developing computerized patient registries, team and staff turnover, and occasional need for more support by senior management. CONCLUSIONS: The Health Disparities Collaborative improved diabetes care in health centers in 1 year.

Dipole and quadrupole moment functions of the hydrogen halides HF, HCl, HBr, and HI: a Hirshfeld interpretation.

The dipole and quadrupole moment functions of the hydrogen halides are calculated using a large polarized basis and correlated wavefunctions and compared to experiment and previous calculations. These functions are analyzed in terms of local moments constructed using the Hirshfeld method. The dipole moment is the sum of the functions q(H)R+mu(H) and mu(X) with q(H) being the charge on the hydrogen atom, R the internuclear separation, mu(H) and mu(X) the atomic dipoles on the hydrogen and halogen atoms. We find that q(H)R+mu(H) is always positive and has a maximum at bond lengths larger than the equilibrium. In HF, mu(F) is slightly positive at the maximum in q(H)R+mu(H) and has little effect on the resultant maximum in the dipole moment function (DMF). mu(Cl), mu(Br), and mu(I), on the other hand, are increasingly more negative at the maximum of q(H)R+mu(H) and have a profound effect on the width of the maximum of the resulting DMF, successively broadening it and completely eliminating it at HI. The quadrupole moment function (QMF) (with the halogen as origin) is given by Theta(HX)=Theta(HX) (proto)+deltaTheta(X)+deltaTheta(H)+2mu(H)R+q(H)R(2), where Theta(HX) (proto) is the quadrupole moment of the separated atoms (the halogen in this instance) and deltaTheta(X)+deltaTheta(H) the change in the in situ quadrupole moments of the halogen and hydrogen atoms. The maximum in the QMF and its slope at equilibrium are determined essentially by 2mu(H)R+q(H)R(2), which is known once the DMF is known. deltaTheta(X)+deltaTheta(H) is always negative while Theta(HX) (proto) is positive, so one can approximate the molecular quadrupole moment to within 10% as Theta(HX)>Theta(HX) (proto)+2mu(H)R+q(H)R(2).

Relationship between the charge distribution and dipole moment functions of CO and the related molecules CS, SiO, and SiS.

The dipole moment functions of the titled molecules are written as the sum of a charge and induced atomic dipole contribution and the distance dependence interpreted in terms of these components. These two contributions have opposite signs over a large range of internuclear distances, and when they have equal magnitudes, the dipole moment vanishes. This happens with CO near the equilibrium bond length and is responsible for its small dipole moment. The dipole moment of CS is 0.770(ea0), rather large for a diatomic in which the two atoms have essentially the same electronegativities; this is because for CS, the two components of the dipole moment have the same sign at equilibrium and reinforce one another.

On the representation of molecular quadrupole moments in terms of atomic moments.

The magnitude and algebraic sign of the molecular quadrupole moments of the homonuclear diatomic molecules N2, O2, F2, P2, S2 and Cl2 are analyzed by expressing them as a sum of the quadrupole moments of the free atoms and an induced molecular quadrupole due to bond formation. This induced molecular quadrupole is further analyzed in terms of in situ atomic dipole and quadrupole moments constructed following the electron partitioning method suggested by Hirshfeld. These in situ moments are interpreted in terms of the sigma and pi character of the chemical bonds and are compared with those predicted by the DMA method of Stone (The Theory of Intermolecular Forces; Clarendon: Oxford, 1996).

Investigation of transition metal-imido bonding in M(NBut)2(dpma).

A complete series down group 6 of the formula M(NBu(t))(2)(dpma) has been synthesized, where dpma is N,N-di(pyrrolyl-alpha-methyl)-N-methylamine. A fourth complex, Mo(NAr)(2)(dpma) (4), was also prepared, where Ar is 2,6-diisopropylphenyl. All four of these complexes display geometries in the solid state best described as square pyramidal with one imido ligand occupying the axial position and the other an equatorial site. In all cases, the axial imido ligand has a significantly smaller M-N(imido)-C bond angle with respect to the equatorial multiple-bond substituent. From the (1)H, (13)C, and (14)N NMR spectra, the axial (bent) imido appears to be more electron-rich than the equatorial and linear imido, with the differences becoming less pronounced down the column. The angular deformation energies for the axial imido ligands were studied by DFT in order to discern if and to what extent imido bond angles were important energetically. The electronic energies associated with straightening the axial imido ligand, while holding the remainder of the molecule at the ground-state geometry, for the Cr, Mo, and W derivatives were calculated as 4.5, 2.7, and 2.0 kcal/mol, respectively. A straight-line plot is found for deformation energies versus estimated electronegativity of the group 6 metals in the +6 oxidation state. The study suggests that the electronic differences between metal imido ligands of different angles are quite small; however, the effects may be more pronounced for metal centers with higher electronegativity, e.g. Cr(VI) with electron-withdrawing ligands.

Barium azacryptand sodide, the first alkalide with an alkaline Earth cation, also contains a novel dimer, (Na(2))(2-).

The first barium sodide, with stoichiometry Ba(2+)(H(5)Azacryptand[2.2.2](-))Na(-).2MeNH(2), was synthesized by the reaction of Ba, Na, and H(6)Azacryptand[2.2.2] in NH(3)-MeNH(2) solution. It was characterized by X-ray crystallography, (23)Na MAS NMR, hydrogen evolution, DSC, optical spectroscopy, and magnetic susceptibility. This is the first sodide in which the sodium anions form (Na(2))(2)(-) dimers. Previous theoretical predictions were verified by a calculation of the potential energy curve for the dimer in the field of the surrounding charges, whose positions were determined from the crystal structure.