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Latent Transition Analysis of Pre-service Teachers' Efficacy in Mathematics and Science (open access)

Latent Transition Analysis of Pre-service Teachers' Efficacy in Mathematics and Science

This study modeled changes in pre-service teacher efficacy in mathematics and science over the course of the final year of teacher preparation using latent transition analysis (LTA), a longitudinal form of analysis that builds on two modeling traditions (latent class analysis (LCA) and auto-regressive modeling). Data were collected using the STEBI-B, MTEBI-r, and the ABNTMS instruments. The findings suggest that LTA is a viable technique for use in teacher efficacy research. Teacher efficacy is modeled as a construct with two dimensions: personal teaching efficacy (PTE) and outcome expectancy (OE). Findings suggest that the mathematics and science teaching efficacy (PTE) of pre-service teachers is a multi-class phenomena. The analyses revealed a four-class model of PTE at the beginning and end of the final year of teacher training. Results indicate that when pre-service teachers transition between classes, they tend to move from a lower efficacy class into a higher efficacy class. In addition, the findings suggest that time-varying variables (attitudes and beliefs) and time-invariant variables (previous coursework, previous experiences, and teacher perceptions) are statistically significant predictors of efficacy class membership. Further, analyses suggest that the measures used to assess outcome expectancy are not suitable for LCA and LTA procedures.
Date: December 2009
Creator: Ward, Elizabeth Kennedy
System: The UNT Digital Library
Slaves and Slaveholders in the Choctaw Nation: 1830-1866 (open access)

Slaves and Slaveholders in the Choctaw Nation: 1830-1866

Racial slavery was a critical element in the cultural development of the Choctaws and was a derivative of the peculiar institution in southern states. The idea of genial and hospitable slave owners can no more be conclusively demonstrated for the Choctaws than for the antebellum South. The participation of Choctaws in the Civil War and formal alliance with the Confederacy was dominantly influenced by the slaveholding and a connection with southern identity, but was also influenced by financial concerns and an inability to remain neutral than a protection of the peculiar institution. Had the Civil War not taken place, the rate of Choctaw slave ownership possibly would have reached the level of southern states and the Choctaws would be considered part of the South.
Date: May 2009
Creator: Fortney, Jeffrey L., Jr.
System: The UNT Digital Library
Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model (open access)

Predicting Chemical and Biochemical Properties Using the Abraham General Solvation Model

Several studies were done to illustrate the versatillity of the Abraham model in mathematically describing the various solute-solvent interactions found in a wide range of different chemical and biological systems. The first study focused on using the solvation model to construct mathematical correlations describing the minimum inhibitory concentration of organic compounds for growth inhibition towards the three bacterial strains Porphyromonas gingivalis, Selenomonas artemidis, and Streptococcus sobrinus. The next several studies expand the practicallity of the Abraham model by predicting free energies of partition in chemical systems. The free energy studies expand the use of the Abraham model to other temperatures and properties by developing correlations for the enthalpies of solvation of gaseous solutes of various compounds dissolved in water, 1-octanol, hexane, heptane, hexadecane, cyclohexane, benzene, toluene, carbon tetrachloride, chloroform, methanol, ethanol, 1-butanol, propylene carbonate, dimethyl sulfoxide, 1,2-dichloroethane, N,N-dimethylformamide, tert-butanol, dibutyl ether, ethyl acetate, acetonitrile, and acetone. Also, a generic equation for linear alkanes is created for use when individual datasets are small. The prediction of enthalpies of solvation is furthered by modifying the Abraham model so that experimental data measured at different temperatures can be included into a single correlation expression. The temperature dependence is directly included in the model …
Date: May 2009
Creator: Mintz, Christina
System: The UNT Digital Library
Grounds-Based and Grounds-Free Voluntarily Child Free Couples: Privacy Management and Reactions of Social Network Members (open access)

Grounds-Based and Grounds-Free Voluntarily Child Free Couples: Privacy Management and Reactions of Social Network Members

Voluntarily child free (VCF) individuals face stigmatization in a pronatalist society that labels those who do not want children as deviant. Because of this stigmatization, VCF couples face privacy issues as they choose to reveal or conceal their family planning decision and face a variety of reactions from social network members. Therefore, communication privacy management and communication accommodation theory was use to examine this phenomenon. Prior research found two different types of VCF couples: grounds-based and grounds-free. Grounds-based individuals cite medical or biological reasons for not having children, while grounds-free individuals cite social reasons for not having children. The purpose of this study is to examine how grounds-based and grounds-free VCF couples manage their disclosure of private information and how social network members react to their family planning decision. Findings revealed that grounds-free individuals are more likely to engage in the self-defense hypothesis and grounds-based individuals are more likely to engage in the expressive need hypothesis. Grounds-based individuals were asked about their decision in dyadic situations, whereas grounds-free individuals were asked at group gatherings. Additionally, social network members used under-accommodation strategies the most frequently and grounds-free individuals experienced more name calling than grounds-based. Finally, while grounds-free individuals experienced non-accommodation and …
Date: May 2009
Creator: Regehr, Kelly A.
System: The UNT Digital Library
Primary Stylistic Characteristics of Cindy McTee's Music as found in Timepiece, Ballet for Band and Finish Line (open access)

Primary Stylistic Characteristics of Cindy McTee's Music as found in Timepiece, Ballet for Band and Finish Line

Cindy McTee, Regents Professor of Composition in the College of Music at the University of North Texas, is one of America's leading composers. Her music is an eclectic blend of the "American" sound that is created by the use of a multiplicity of techniques. This document uses three of McTee's most recent (to date) works for wind band: Timepiece, Ballet for Band and Finish Line, to identify the primary stylistic characteristic's of the composer's music, which include: jazz influence; use of ostinati, pseudo-ostinati and machine-like rhythmic patterns and figures; creation of extended and angular melodic lines; progressive "walking" bass lines; and the use of octatonic and chromatic collections. Through the identification of stylistic characteristics, concise stylistic analysis of the works, interview transcript, list of composer's works to date, and selected discography, this document will add to the limited body of scholarly writing on the composer.
Date: May 2009
Creator: Williams, Nicholas, 1974-
System: The UNT Digital Library
Level Curves of the Angle Function of a Positive Definite Symmetric Matrix (open access)

Level Curves of the Angle Function of a Positive Definite Symmetric Matrix

Given a real N by N matrix A, write p(A) for the maximum angle by which A rotates any unit vector. Suppose that A and B are positive definite symmetric (PDS) N by N matrices. Then their Jordan product {A, B} := AB + BA is also symmetric, but not necessarily positive definite. If p(A) + p(B) is obtuse, then there exists a special orthogonal matrix S such that {A, SBS^(-1)} is indefinite. Of course, if A and B commute, then {A, B} is positive definite. Our work grows from the following question: if A and B are commuting positive definite symmetric matrices such that p(A) + p(B) is obtuse, what is the minimal p(S) such that {A, SBS^(-1)} indefinite? In this dissertation we will describe the level curves of the angle function mapping a unit vector x to the angle between x and Ax for a 3 by 3 PDS matrix A, and discuss their interaction with those of a second such matrix.
Date: December 2009
Creator: Bajracharya, Neeraj
System: The UNT Digital Library
An Evaluation of the Effects of Two Different Role Play Formats on the Outcomes of a Parent Training Curriculum (open access)

An Evaluation of the Effects of Two Different Role Play Formats on the Outcomes of a Parent Training Curriculum

The current study was designed to replicate and extend previous research on the effectiveness of behavioral parent training. Specifically, the effectiveness of the Behavior Management and Parenting Services (BMAPS) curriculum in teaching parents to exhibit a set of parenting skills and respond accurately to a multiple choice examination about positive parenting techniques was evaluated. In addition, the curriculum was revised so that the relative effectiveness and acceptability of two role play formats could be assessed. The outcomes of the study showed an improvement in the participants' ability to identify correct answers on a multiple choice examination and apply the parenting skills taught in class within a role play format; results pertaining to the efficacy of each role play format were less conclusive.
Date: December 2009
Creator: Carlson Litscher, Barbara J.
System: The UNT Digital Library
Learner-to-Learner: Refocusing the Lens of Educational Immediacy (open access)

Learner-to-Learner: Refocusing the Lens of Educational Immediacy

As the current body of instructional communication research focuses primarily on the relationship between teacher and learner, three studies investigating the relationship between learners were completed in order to better understand how student motivation and learning are influenced by learner-to-learner immediacy behaviors within the college classroom environment. Study I resulted in an extensive list of both positive and negative verbal and nonverbal immediacy behaviors commonly used by learners. Study II required the comparison of the behaviors identified in study one to existing measures of teacher to learner immediacy behaviors, producing a new measure focusing on learner-to-learner immediacy. Following a pilot survey, the reliability of this new measure was determined through face validity and factor analysis, producing the Learner-to-Learner Immediacy Behavior Scale. In Study III, the Learner-to-Learner Immediacy Behavior Scale was combined with Christophel's 1990 Immediacy Behavior Scale, Cognitive Learning Scale, Affective Learning Scale, and Trait and State Motivation Scales and administered to 273 undergraduate students to test the affects of common learner-to-learner immediacy behaviors on student state motivation, affective learning, and perceptions of cognitive learning loss. Multiple regression analyses indicated learner-to-learner immediacy as functioning similarly to teacher-to-student immediacy when mediated through state motivation in its influence on student affective learning …
Date: May 2009
Creator: Keller, Christine Ida
System: The UNT Digital Library
A New Wireless Sensor Node Design for Program Isolation and Power Flexibility (open access)

A New Wireless Sensor Node Design for Program Isolation and Power Flexibility

Over-the-air programming systems for wireless sensor networks have drawbacks that stem from fundamental limitations in the hardware used in current sensor nodes. Also, advances in technology make it feasible to use capacitors as the sole energy storage mechanism for sensor nodes using energy harvesting, but most current designs require additional electronics. These two considerations led to the design of a new sensor node. A microcontroller was chosen that meets the Popek and Goldberg virtualization requirements. The hardware design for this new sensor node is presented, as well as a preliminary operating system. The prototypes are tested, and demonstrated to be sustainable with a capacitor and solar panel. The issue of capacitor leakage is considered and measured.
Date: December 2009
Creator: Skelton, Adam W.
System: The UNT Digital Library
Racial Stereotypes and Racial Assimilation in a Multiracial Society (open access)

Racial Stereotypes and Racial Assimilation in a Multiracial Society

Interest in a multiracial society has increased in recent years and including on racism and prejudice and in the propensity to stereotype out-groups. Theories on racism help explain the dominant group's prejudice toward subordinate groups. Yet they only explain why dominant group members stereotype subordinates or if the dominant group's propensity to stereotype is different from that of subordinate groups. Recent assimilation theories suggest that some minorities are assimilating with Whites but Blacks are not undergoing assimilation. Classic assimilation theory suggests that when a subordinate group assimilates with the dominant group then they will also take on the dominant group's values and beliefs, including their prejudices and propensities to stereotype. The use of racial stereotypes in support of the assimilation of a minority group has not been tested. Results from the LSAF national survey provide support for Asians to be assimilating with Whites. However, Hispanics do not appear to be taking on Whites' propensity to stereotype, contradicting the prediction that Hispanics are assimilating with Whites.
Date: December 2009
Creator: Youngblood, Thomas
System: The UNT Digital Library
Survey of Approximation Algorithms for Set Cover Problem (open access)

Survey of Approximation Algorithms for Set Cover Problem

In this thesis, I survey 11 approximation algorithms for unweighted set cover problem. I have also implemented the three algorithms and created a software library that stores the code I have written. The algorithms I survey are: 1. Johnson's standard greedy; 2. f-frequency greedy; 3. Goldsmidt, Hochbaum and Yu's modified greedy; 4. Halldorsson's local optimization; 5. Dur and Furer semi local optimization; 6. Asaf Levin's improvement to Dur and Furer; 7. Simple rounding; 8. Randomized rounding; 9. LP duality; 10. Primal-dual schema; and 11. Network flow technique. Most of the algorithms surveyed are refinements of standard greedy algorithm.
Date: December 2009
Creator: Dutta, Himanshu Shekhar
System: The UNT Digital Library
God's Perfect Timing (open access)

God's Perfect Timing

When I was thirty-three years old, I discovered I was an adoptee. In this memoir of secrecy and love, betrayal and redemption, I reflect on my early experiences as a doted-on only child firmly rooted in the abundant love of my adoptive family, my later struggles with depression and obsessive-compulsive disorder, my marriage to a fellow-adoptee, my discovery of my own adoption and the subsequent reunion with my birth family, my navigation through the thrills and tensions of newly complicated family dynamics, and my witness to God's perfect timing through it all.
Date: August 2009
Creator: Rizzo, Steven
System: The UNT Digital Library
The Other Side of Yesterday (open access)

The Other Side of Yesterday

The four stories in this collection follow different, yet strikingly similar, protagonists who are facing crossroads in life. These stories include memories and specific scenes from the past that combine with scenes from the present to trace the development of the characters.
Date: May 2009
Creator: Rose, John
System: The UNT Digital Library
An Evaluation Model for Identifying Lewisville and San Angelo, Texas, as Senior Ready Communities (open access)

An Evaluation Model for Identifying Lewisville and San Angelo, Texas, as Senior Ready Communities

This research portrays a paradigm for the assessment of aging services to support populations aging in place. The dissertation was designed to establish a model to identify and evaluate senior ready communities. Area specific social programs and services are identified. In order to meet the growing needs of aging populations, the dynamic representation of existing services and the need for services that could be developed in certain communities require reevaluation in current planning, restructuring, and/or community development.
Date: December 2009
Creator: Sanders, David N.
System: The UNT Digital Library
An Investigation Into the Factors Leading to the Closure of 40 Private Four-Year Colleges between 1965 and 2005 (open access)

An Investigation Into the Factors Leading to the Closure of 40 Private Four-Year Colleges between 1965 and 2005

This study searches for a set of common indicators that contributed to the ultimate closure of 40 colleges and universities between 1965 and 2005. From research on related literature, a set of 31 contributing factors was identified by published experts and observers in higher education. That set of indicators was then used as a list of 31 questions answered by data found in newspaper articles, professional journals, published research work, published institutional records, data taken from the Department of Education, data taken from IPEDS, data published in historical recounts of the colleges of interest, etc. The data was accumulated in the form of yes/no responses to the 31 questions. Although the study involved only 40 colleges and universities this population represents the majority of institutions that pass the restrictions of limitations and delimitations described in the full document. The complete data set was processed using SPSS which produced ANOVA tables and level of statistical significance for each indicator question. The results indicate that out of the 31 original indicator questions there were two groups of statistically significant indicators. The larger group of indicators having statistical significance at the .05 level encompassed the smaller group having statistical significance at the .001 …
Date: December 2009
Creator: Province, Terry Paul
System: The UNT Digital Library
Health Status and Access Disparities Among the Uninsured Working-Age Population in a Safety-Net Healthcare Network in Tarrant County, Texas (open access)

Health Status and Access Disparities Among the Uninsured Working-Age Population in a Safety-Net Healthcare Network in Tarrant County, Texas

The objective of this research was to determine if healthcare access disparities exist across race and gender in a publically funded safety-net healthcare system in Texas. Data were examined from a representative random sample of 1468 adults aged 18-64 who were patients in this safety-net system in July and August of 2000 and were analyzed using binary logistic regression and chi-square measures of significance. Major Findings: On measures of health status - overall health rating (p =.051), limited employment (p =.000), energy level (p =.001), and worry (p =.012) - Anglos reported the worst health; Mexican Americans, the best health; with African Americans intermediate. Mexican Americans were more likely to have never had health insurance, and to also have had insurance in the past year; Anglos were least likely to have ever had insurance (p =.015) or to have had insurance in the past year (p =.000). On use of EDs (p =.028), problems getting prescription medicines (p =.029), and foregoing other necessities of life to pay for healthcare, Mexican Americans were least disadvantaged with African Americans reporting greatest use of EDs among both men and women, and Anglos the most problems with prescription medicines and foregoing care, especially among …
Date: December 2009
Creator: Queen, Courtney M.
System: The UNT Digital Library
High Resolution Satellite Images and LiDAR Data for Small-Area Building Extraction and Population Estimation (open access)

High Resolution Satellite Images and LiDAR Data for Small-Area Building Extraction and Population Estimation

Population estimation in inter-censual years has many important applications. In this research, high-resolution pan-sharpened IKONOS image, LiDAR data, and parcel data are used to estimate small-area population in the eastern part of the city of Denton, Texas. Residential buildings are extracted through object-based classification techniques supported by shape indices and spectral signatures. Three population indicators -building count, building volume and building area at block level are derived using spatial joining and zonal statistics in GIS. Linear regression and geographically weighted regression (GWR) models generated using the three variables and the census data are used to estimate population at the census block level. The maximum total estimation accuracy that can be attained by the models is 94.21%. Accuracy assessments suggest that the GWR models outperformed linear regression models due to their better handling of spatial heterogeneity. Models generated from building volume and area gave better results. The models have lower accuracy in both densely populated census blocks and sparsely populated census blocks, which could be partly attributed to the lower accuracy of the LiDAR data used.
Date: December 2009
Creator: Ramesh, Sathya
System: The UNT Digital Library
The Effects of Attendance at a Senior Center on the Quality of Life and Well Being of Grandparents Rearing Grandchildren. (open access)

The Effects of Attendance at a Senior Center on the Quality of Life and Well Being of Grandparents Rearing Grandchildren.

The purpose of this study was to determine the effects of attendance at a senior center on the well being and quality of life of grandparents that were rearing grandchildren. Using convenience sampling, grandparents (N=130) who were rearing grandchildren were given a self administered demographic data survey along with an attendance at a senior center questionnaire, the Quality of Life Scale, the Well Being Scale by Liang, the UCLA Loneliness Scale, the Caregiver Burden Scale, and the Role Satisfaction Scale. An initial MANOVA (F 7, 69 = 2.72, p < .01) suggesting that senior center attendance affect the measures as a set was conducted and then a series of one way ANOVAs were carried out to test the hypothesis that attending a senior center has an effect on the dependent variables: well being, quality of life, role satisfaction, caregiver burden, loneliness, current health, and heath one year ago. Subsequently, a hierarchical regression analysis was conducted to find out whether frequency and quality of attendance of a senior center predicted quality of life, caregiver burden, well being, loneliness, and role satisfaction, controlling for the demographic data. The results of the MANOVA showed that the dependent variables: quality of life, caregiver burden, …
Date: December 2009
Creator: Rhynes, LaTrica Q.
System: The UNT Digital Library
Victimization and expressions of relational and overt aggression among boys and girls with ADHD. (open access)

Victimization and expressions of relational and overt aggression among boys and girls with ADHD.

This study investigated if girls and boys high in ADHD symptomology exhibited and experienced relational and overt aggression differently than boys and girls without ADHD symptoms using peer, parent and teacher ratings. A measurement of social behavior for parent ratings was also validated. Using archival data, 371 3rd- 6th graders from a north Texas school district participated in the study, along with a parent or guardian and teachers. Results supported that ADHD subtype predicted more overt aggression according to parents and teachers but not peers. ADHD subtype did not predict more relational aggression but ADHD symptomology did. Contrary to past research, gender did not moderate relational aggression or internalizing symptoms from relational victimization. Furthermore, a parent version of the Child Social Behavior Scale was found to effectively measure relational, overt and prosocial behavior. Limitations, future directions and implications are discussed.
Date: December 2009
Creator: Rivero, Arlene Jean Abello
System: The UNT Digital Library
Inferring Social and Internal Context Using a Mobile Phone (open access)

Inferring Social and Internal Context Using a Mobile Phone

This dissertation is composed of research studies that contribute to three research areas including social context-aware computing, internal context-aware computing, and human behavioral data mining. In social context-aware computing, four studies are conducted. First, mobile phone user calling behavioral patterns are characterized in forms of randomness level where relationships among them are then identified. Next, a study is conducted to investigate the relationship between the calling behavior and organizational groups. Third, a method is presented to quantitatively define mobile social closeness and social groups, which are then used to identify social group sizes and scaling ratio. Last, based on the mobile social grouping framework, the significant role of social ties in communication patterns is revealed. In internal context-aware computing, two studies are conducted where the notions of internal context are intention and situation. For intentional context, the goal is to sense the intention of the user in placing calls. A model is thus presented for predicting future calls envisaged as a call predicted list (CPL), which makes use of call history to build a probabilistic model of calling behavior. As an incoming call predictor, CPL is a list of numbers/contacts that are the most likely to be the callers within …
Date: December 2009
Creator: Phithakkitnukoon, Santi
System: The UNT Digital Library
Design and Validation of an Automated Multiunit Composting System. (open access)

Design and Validation of an Automated Multiunit Composting System.

This thesis covers the design of an automated multiunit composting system (AMUCS) that was constructed to meet the experimental apparatus requirements of the ASTM D5338 standard. The design of the AMUCS is discussed in full detail and validated with two experiments. The first experiment was used to validate the operation of the AMUCS with a 15 day experiment. During this experiment visual observations were made to visually observe degradation. Thermal properties and stability tests were performed to quantify the effects of degradation on the polymer samples, and the carbon metabolized from the degradation of samples was measured. The second experiment used the AMUCS to determine the effect of synthetic clay nanofiller on the aerobic biodegradability behavior of poly (3-hydroxybutyrate-co-3-hydroxyvalerate).
Date: December 2009
Creator: Pickens, Mark Everett
System: The UNT Digital Library
Does the Knowledge of Unaudited Account Balances Adversely Affect the Performance of Substantive Analytical Procedures? (open access)

Does the Knowledge of Unaudited Account Balances Adversely Affect the Performance of Substantive Analytical Procedures?

Auditors use substantive analytical procedures to make assertions about the adequacy and appropriateness of client balances. The analytical procedure process consists of auditors creating independent account expectations and corroborating unusual fluctuations through obtaining and evaluating additional audit evidence. Prior analytical procedure research has found that knowledge of clients' unaudited account balances biases auditors' expectations towards the current year figures. However, this research has failed to examine the impact of biased expectations on the subsequent stages of analytical procedures. This dissertation assesses the full impact of biased account expectations on auditors' use of analytical procedures. I experimentally test the hypotheses of my dissertation through administering an experiment to senior level auditors. After inducing an account expectation bias that favors the client account balance in half the participants, I examine the auditors' cognitive investigation into an unusual account fluctuation. The results indicate that a biased account expectation negatively affects auditors' judgment quality. In particular, a biased expectation leads auditors to favor hypotheses and additional information that supports the proposition that the client's balance is reasonably stated. Alternatively, auditors with unbiased account expectations are more willing to consider all hypotheses and are able to identify the most pertinent additional information to the decision …
Date: December 2009
Creator: Pike, Byron J.
System: The UNT Digital Library
The perception of English language arts teachers about instructional changes following the implementation of the Texas Assessment of Knowledge and Skills test. (open access)

The perception of English language arts teachers about instructional changes following the implementation of the Texas Assessment of Knowledge and Skills test.

Accountability in education has been expanding for the past twenty years. As standards for curricular areas continued to develop, educational shareholders desired a way to measure student achievement contextualized by the established standards. Since 1964, policies expanded federal involvement with education, and with the No Child Left Behind Act in 2001, high-stakes testing became a significant part of public education. In Texas, testing transitioned in 2003 to the Texas Assessment of Knowledge and Skill (TAKS) test, an assessment that determines grade advancement for students, ratings for school districts, and additional compensation for some teachers. Along with the increasing expectations for student achievement, the need for effective instruction also increases. This dissertation studies how English language arts (ELA) teachers in four North Texas suburban high schools perceive instructional change following the implementation of TAKS. One hundred twenty-one teachers (n=121) were surveyed using an instrument broken into seven categories: student-centered instruction, student interest, instructional communication, time, classroom environment, teacher knowledge, and assessment. Participants were separated into two groups, teachers with one to six years of experience with a district or seven or more years with a district. Using a rating scale for each statement on the survey instrument, participants indicated the direction …
Date: December 2009
Creator: Horn, Brian K.
System: The UNT Digital Library
Synthesis and Characterization of Platinum(II)(2-(9-anthracenylylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione)(dichloride), Platinum(II)(2-(9-anthracenylylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione(maleonitriledithiolate), and Platinum(II)(4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione)(4-Methyl-1,2-benzene dithiol) (open access)

Synthesis and Characterization of Platinum(II)(2-(9-anthracenylylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione)(dichloride), Platinum(II)(2-(9-anthracenylylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione(maleonitriledithiolate), and Platinum(II)(4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione)(4-Methyl-1,2-benzene dithiol)

Substitution of the 1,5-cyclooctadiene (cod) ligand in PtCl2(cod) (1) by the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) yields PtCl2(bpcd) (2). Knoevenagel condensation of 2 with 9-anthracenecarboxaldehyde leads to the functionalization of the bpcd ligand and formation of the corresponding 2-(9-anthracenylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (abpcd) substituted compound PtCl2(abpcd) (3), which is also obtained from the direct reaction of 1 with the abpcd ligand in near quantitative yield. The reaction of 3 with disodium maleonitriledithiolate (Na2mnt) affords the chelating dithiolate compound Pt(mnt)(abpcd) (4). The reaction of PtCl2(bpcd) (2) with 4-methyl-1,2-benzene dithiol under basic conditions affords Pt(tdt)(bpcd) (5). Compounds 2-5 have been fully characterized in solution by IR and NMR spectroscopies (1H and 31P), and their molecular structures established by X-ray crystallography. The electrochemical properties of 2&#8209;5 have examined by cyclic voltammetry, and the nature of the HOMO and LUMO levels in systems 2-4 has been established by MO calculations at the extended Hückel level, the results of which are discussed with respect to electrochemical data and related diphosphine derivatives. In addition the new compounds 2-5 have been isolated by column chromatography and characterized by IR, UV-Vis spectroscopy.
Date: December 2009
Creator: Hunt, Sean W.
System: The UNT Digital Library